{"format":"molecular-machines.cards","version":1,"updated":"2026-10-01","decks":[{"machine":"groel","name":"GroEL–GroES","count":28,"url":"/learn/cards/groel.json"}],"cards":[{"id":"groel-what-it-does","machine":"groel","kind":"qa","prompt":"What does GroEL do for a protein that has not folded?","answer":"It closes the protein in a chamber where it folds alone, safe from aggregation.","explanation":"Hydrophobic surfaces in one ring catch the protein; ATP and the lid GroES then close the chamber around it.","section":"summary","topic":"purpose","sources":["machine:summary","mechanism:Folding in isolation","ref:weissman1996"],"tags":["folding","aggregation"],"difficulty":1,"url":"/machines/groel#summary","cites":[{"source":"machine:summary","machine":"groel","label":"Summary","section":"summary"},{"source":"mechanism:Folding in isolation","machine":"groel","label":"Step: Folding in isolation","section":"mechanism"},{"source":"ref:weissman1996","machine":"groel","label":"Weissman et al.","section":"sources","anchor":"ref-weissman1996","href":"https://doi.org/10.1016/s0092-8674(00)81293-3"}]},{"id":"groel-equatorial-domain-role","machine":"groel","kind":"qa","prompt":"Which GroEL domain binds ATP and holds the two rings together?","answer":"The equatorial domain.","explanation":"Each GroEL subunit has three domains: equatorial (ATP, ring contacts), intermediate (the hinge) and apical (binds substrate and GroES).","section":"summary","topic":"parts","sources":["component:GroEL equatorial domain","evidence:groel-fourteen-subunits","ref:braig1994"],"tags":["domains","atp"],"difficulty":1,"url":"/machines/groel#summary","cites":[{"source":"component:GroEL equatorial domain","machine":"groel","label":"Part: GroEL equatorial domain","section":"summary"},{"source":"evidence:groel-fourteen-subunits","machine":"groel","label":"Subunit architecture of GroEL (Braig K 1994)","section":"evidence","anchor":"ev-groel-fourteen-subunits"},{"source":"ref:braig1994","machine":"groel","label":"Braig et al.","section":"sources","anchor":"ref-braig1994","href":"https://doi.org/10.1038/371578a0"}]},{"id":"groel-apical-helices-h-i","machine":"groel","kind":"qa","prompt":"Through which helices does the GroEL apical domain bind both the unfolded substrate and GroES?","answer":"Helices H and I.","explanation":"The same sites hold the client first and GroES later, so GroES binding takes the sites away from the client.","section":"summary","topic":"parts","sources":["component:GroEL apical domain","step:GroES closes the new chamber","ref:clare2012"],"tags":["domains","binding"],"difficulty":2,"url":"/machines/groel#summary","cites":[{"source":"component:GroEL apical domain","machine":"groel","label":"Part: GroEL apical domain","section":"summary"},{"source":"step:GroES closes the new chamber","machine":"groel","label":"Step: GroES closes the new chamber","section":"mechanism"},{"source":"ref:clare2012","machine":"groel","label":"Clare et al.","section":"sources","anchor":"ref-clare2012","href":"https://doi.org/10.1016/j.cell.2012.02.047"}]},{"id":"groel-thermosome-built-in-lid","machine":"groel","kind":"qa","prompt":"Why does the archaeal thermosome, a group II chaperonin, need no GroES lid?","answer":"Its own apical domains form a built-in lid.","explanation":"Group I chaperonins such as GroEL, in bacteria and organelles, use a separate GroES lid. The thermosome also has eight subunits per ring, not seven.","section":"summary","topic":"parts","sources":["species:Thermosome","evolution:Two chaperonin groups","ref:ditzel1998"],"tags":["evolution","lid"],"difficulty":2,"url":"/machines/groel#summary","cites":[{"source":"species:Thermosome","machine":"groel","label":"Thermosome","section":"summary"},{"source":"evolution:Two chaperonin groups","machine":"groel","label":"Two chaperonin groups","section":"summary"},{"source":"ref:ditzel1998","machine":"groel","label":"Ditzel et al.","section":"sources","anchor":"ref-ditzel1998","href":"https://doi.org/10.1016/s0092-8674(00)81152-6"}]},{"id":"groel-seven-per-ring","machine":"groel","kind":"cloze","prompt":"GroEL is a cylinder of two stacked rings, each made of {{seven}} subunits.","answer":"seven","explanation":"That gives 14 GroEL subunits, capped by one GroES ring of 7 subunits (X-ray structure, Braig et al. 1994).","section":"summary","topic":"numbers","sources":["stat:Subunits","evidence:groel-fourteen-subunits","ref:braig1994"],"tags":["structure"],"difficulty":1,"url":"/machines/groel#summary","cites":[{"source":"stat:Subunits","machine":"groel","label":"Key number: Subunits","section":"summary"},{"source":"evidence:groel-fourteen-subunits","machine":"groel","label":"Subunit architecture of GroEL (Braig K 1994)","section":"evidence","anchor":"ev-groel-fourteen-subunits"},{"source":"ref:braig1994","machine":"groel","label":"Braig et al.","section":"sources","anchor":"ref-braig1994","href":"https://doi.org/10.1038/371578a0"}]},{"id":"groel-size-limit","machine":"groel","kind":"cloze","prompt":"The closed GroEL–GroES chamber can hold unfolded proteins up to about {{60 kDa}}.","answer":"60 kDa","explanation":"Denatured proteins smaller than the 57 kDa GroEL subunit stay inside; an 82 kDa protein binds GroEL but never enters.","section":"summary","topic":"numbers","sources":["stat:Substrate size limit","ref:sakikawa1999"],"tags":["chamber","size"],"difficulty":2,"url":"/machines/groel#summary","cites":[{"source":"stat:Substrate size limit","machine":"groel","label":"Key number: Substrate size limit","section":"summary"},{"source":"ref:sakikawa1999","machine":"groel","label":"Sakikawa et al.","section":"sources","anchor":"ref-sakikawa1999","href":"https://doi.org/10.1074/jbc.274.30.21251"}]},{"id":"groel-atp-per-cycle","machine":"groel","kind":"qa","prompt":"How many ATP does one GroEL ring bind and hydrolyse in each folding cycle?","answer":"7","explanation":"One ATP per subunit of the ring. Each turn of the alternating-ring cycle uses one ringful of ATP (Rye et al. 1999).","section":"summary","topic":"numbers","sources":["stat:ATP per folding cycle","machine:energy","ref:rye1999"],"tags":["atp"],"difficulty":1,"url":"/machines/groel#summary","cites":[{"source":"stat:ATP per folding cycle","machine":"groel","label":"Key number: ATP per folding cycle","section":"summary"},{"source":"machine:energy","machine":"groel","label":"Summary","section":"summary"},{"source":"ref:rye1999","machine":"groel","label":"Rye et al.","section":"sources","anchor":"ref-rye1999","href":"https://doi.org/10.1016/s0092-8674(00)80742-4"}]},{"id":"groel-evolved-specialist-cost","machine":"groel","kind":"qa","prompt":"What did GroEL/GroES variants evolved to fold green fluorescent protein lose in return?","answer":"General folding ability.","explanation":"The best variant made cells 8-fold brighter with GFP but cut lambda phage plaque formation about 1000-fold. A specialist cage trades away the generalist one.","section":"summary","topic":"debate","sources":["frontier:Chaperonins evolved for one substrate","evidence:evolved-groe-folds-gfp","ref:wang2002"],"tags":["evolution","engineering"],"difficulty":2,"url":"/machines/groel#summary","cites":[{"source":"frontier:Chaperonins evolved for one substrate","machine":"groel","label":"Open question: Chaperonins evolved for one substrate","section":"summary"},{"source":"evidence:evolved-groe-folds-gfp","machine":"groel","label":"Gain and cost of a GFP-optimized GroEL/GroES (Wang JD 2002)","section":"evidence","anchor":"ev-evolved-groe-folds-gfp"},{"source":"ref:wang2002","machine":"groel","label":"Wang et al.","section":"sources","anchor":"ref-wang2002","href":"https://doi.org/10.1016/s0092-8674(02)01198-4"}]},{"id":"groel-capture-hydrophobic","machine":"groel","kind":"qa","prompt":"What does an unfolded protein expose that lets the open GroEL ring catch it?","answer":"Water-repelling (hydrophobic) stretches.","explanation":"These stretches bind a water-repelling collar formed by helices H and I of all seven subunits, with several contacts at once.","section":"mechanism","topic":"cycle","sources":["step:An unfolded protein is caught","mechanism:Capture","ref:braig1994"],"tags":["capture","hydrophobic"],"difficulty":2,"url":"/machines/groel#mechanism","cites":[{"source":"step:An unfolded protein is caught","machine":"groel","label":"Step: An unfolded protein is caught","section":"mechanism"},{"source":"mechanism:Capture","machine":"groel","label":"Step: Capture","section":"mechanism"},{"source":"ref:braig1994","machine":"groel","label":"Braig et al.","section":"sources","anchor":"ref-braig1994","href":"https://doi.org/10.1038/371578a0"}]},{"id":"groel-ring-anticooperativity","machine":"groel","kind":"cloze","prompt":"In GroEL, ATP binding is cooperative within a ring but {{strongly anti-cooperative}} between the two rings.","answer":"strongly anti-cooperative","explanation":"Yifrach and Horovitz fitted an inter-ring Hill coefficient of 0.003. So a ring binds its seven ATP together, and the two rings do not do so at the same time.","section":"mechanism","topic":"cycle","sources":["step:ADP leaves and seven ATP bind","evidence:nested-allostery"],"tags":["atp","allostery"],"difficulty":3,"url":"/machines/groel#mechanism","cites":[{"source":"step:ADP leaves and seven ATP bind","machine":"groel","label":"Step: ADP leaves and seven ATP bind","section":"mechanism"},{"source":"evidence:nested-allostery","machine":"groel","label":"Cooperativity of ATP hydrolysis within and between rings (Yifrach O 1995)","section":"evidence","anchor":"ev-nested-allostery"}]},{"id":"groel-apical-rise-stretches","machine":"groel","kind":"cloze","prompt":"As the GroEL apical domains rise after ATP binds, they stretch the bound protein, which can {{pull misfolded parts apart}}.","answer":"pull misfolded parts apart","explanation":"The apical domains rise and move outwards, so the protein is pulled between its contact points.","section":"mechanism","topic":"cycle","sources":["mechanism:The apical domains rise","step:The apical domains tilt and rise","ref:clare2012"],"tags":["apical","unfolding"],"difficulty":2,"url":"/machines/groel#mechanism","cites":[{"source":"mechanism:The apical domains rise","machine":"groel","label":"Step: The apical domains rise","section":"mechanism"},{"source":"step:The apical domains tilt and rise","machine":"groel","label":"Step: The apical domains tilt and rise","section":"mechanism"},{"source":"ref:clare2012","machine":"groel","label":"Clare et al.","section":"sources","anchor":"ref-clare2012","href":"https://doi.org/10.1016/j.cell.2012.02.047"}]},{"id":"groel-what-opens-old-chamber","machine":"groel","kind":"qa","prompt":"In GroEL, what makes the closed chamber on one ring open and release GroES?","answer":"ATP (with a new client) binding to the opposite ring.","explanation":"The signal crosses the ring contact through the equatorial domains. The old ring lets go of GroES and its protein, folded or not, so the two rings alternate.","section":"mechanism","topic":"cycle","sources":["mechanism:The other ring fires","step:The old chamber opens","ref:rye1999"],"tags":["alternation","release"],"difficulty":2,"url":"/machines/groel#mechanism","cites":[{"source":"mechanism:The other ring fires","machine":"groel","label":"Step: The other ring fires","section":"mechanism"},{"source":"step:The old chamber opens","machine":"groel","label":"Step: The old chamber opens","section":"mechanism"},{"source":"ref:rye1999","machine":"groel","label":"Rye et al.","section":"sources","anchor":"ref-rye1999","href":"https://doi.org/10.1016/s0092-8674(00)80742-4"}]},{"id":"groel-power-stroke-twist","machine":"groel","kind":"qa","prompt":"When GroES docks on GroEL, what does the final twist of about 100° of the apical domains do to the bound client?","answer":"It peels the water-repelling sites off the client and drops it into the chamber.","explanation":"Clare and colleagues call this twist the power stroke of GroEL. It buries the sites against GroES and doubles the chamber volume.","section":"mechanism","topic":"cycle","sources":["step:GroES closes the new chamber","evidence:apical-domain-twist","mechanism:GroES docks and the cage closes","ref:clare2012","ref:xu1997"],"tags":["power-stroke","apical"],"difficulty":3,"url":"/machines/groel#mechanism","cites":[{"source":"step:GroES closes the new chamber","machine":"groel","label":"Step: GroES closes the new chamber","section":"mechanism"},{"source":"evidence:apical-domain-twist","machine":"groel","label":"Final apical-domain rotation that docks GroES (Clare DK 2012)","section":"evidence","anchor":"ev-apical-domain-twist"},{"source":"mechanism:GroES docks and the cage closes","machine":"groel","label":"Step: GroES docks and the cage closes","section":"mechanism"},{"source":"ref:clare2012","machine":"groel","label":"Clare et al.","section":"sources","anchor":"ref-clare2012","href":"https://doi.org/10.1016/j.cell.2012.02.047"},{"source":"ref:xu1997","machine":"groel","label":"Xu et al.","section":"sources","anchor":"ref-xu1997","href":"https://doi.org/10.1038/41944"}]},{"id":"groel-why-no-aggregation-inside","machine":"groel","kind":"qa","prompt":"Why can a protein folding inside the closed GroEL chamber not aggregate?","answer":"The chamber holds only that one protein, so it meets no other chains.","explanation":"The chamber lining is also water-loving, so the folding protein finds nothing sticky.","section":"mechanism","topic":"cycle","sources":["mechanism:Folding in isolation","step:One ring is a closed chamber","ref:weissman1996"],"tags":["chamber","aggregation"],"difficulty":1,"url":"/machines/groel#mechanism","cites":[{"source":"mechanism:Folding in isolation","machine":"groel","label":"Step: Folding in isolation","section":"mechanism"},{"source":"step:One ring is a closed chamber","machine":"groel","label":"Step: One ring is a closed chamber","section":"mechanism"},{"source":"ref:weissman1996","machine":"groel","label":"Weissman et al.","section":"sources","anchor":"ref-weissman1996","href":"https://doi.org/10.1016/s0092-8674(00)81293-3"}]},{"id":"groel-hydrolysis-timer","machine":"groel","kind":"cloze","prompt":"In GroEL, {{ATP hydrolysis}} in the closed ring sets how long the chamber stays shut.","answer":"ATP hydrolysis","explanation":"The ADP state holds GroES less tightly (Rye et al. 1997), and only after hydrolysis can the opposite ring take up a client and GroES (Rye et al. 1999).","section":"mechanism","topic":"cycle","sources":["step:ATP is split: the timer","mechanism:Hydrolysis primes release","ref:rye1997","ref:rye1999"],"tags":["atp","timer"],"difficulty":2,"url":"/machines/groel#mechanism","cites":[{"source":"step:ATP is split: the timer","machine":"groel","label":"Step: ATP is split: the timer","section":"mechanism"},{"source":"mechanism:Hydrolysis primes release","machine":"groel","label":"Step: Hydrolysis primes release","section":"mechanism"},{"source":"ref:rye1997","machine":"groel","label":"Rye et al.","section":"sources","anchor":"ref-rye1997","href":"https://doi.org/10.1038/42047"},{"source":"ref:rye1999","machine":"groel","label":"Rye et al.","section":"sources","anchor":"ref-rye1999","href":"https://doi.org/10.1016/s0092-8674(00)80742-4"}]},{"id":"groel-stuck-chains-clump","machine":"groel","kind":"qa","prompt":"In E. coli, why is a new protein chain that gets stuck half-folded a problem for the cell?","answer":"Its sticky patches can stick to other stuck chains and form a useless clump.","explanation":"Such clumps are useless and can be toxic. GroEL catches stuck chains so they get another chance to fold.","section":"story","topic":"purpose","sources":["stop:chain","story:summary"],"tags":["aggregation","cell"],"difficulty":1,"url":"/machines/groel#story","cites":[{"source":"stop:chain","machine":"groel","label":"Big picture: A new chain","section":"story"},{"source":"story:summary","machine":"groel","label":"Big picture","section":"story"}]},{"id":"groel-share-of-proteins","machine":"groel","kind":"cloze","prompt":"In E. coli during normal growth, about {{10–15%}} of cytoplasmic protein passes through GroEL.","answer":"10–15%","explanation":"Under heat stress the share rises to 30% or more. Most proteins leave GroEL within 10–30 s.","section":"story","topic":"numbers","sources":["fact:G4","ref:ewalt1997"],"tags":["cell","flux"],"difficulty":2,"url":"/machines/groel#story","cites":[{"source":"fact:G4","machine":"groel","label":"Share of cytoplasmic protein that passes through GroEL: 10–15 %","section":"story"},{"source":"ref:ewalt1997","machine":"groel","label":"Ewalt 1997","section":"sources","href":"https://doi.org/10.1016/s0092-8674(00)80509-7"}]},{"id":"groel-essential-for-growth","machine":"groel","kind":"qa","prompt":"How well does E. coli grow without GroEL and GroES?","answer":"Not at all: it cannot grow at any temperature tested.","explanation":"About 85 E. coli proteins need GroEL to fold, and 13 of those are essential to the cell.","section":"story","topic":"purpose","sources":["fact:G8","fact:G7","ref:fayet1989","ref:kerner2005"],"tags":["essential","cell"],"difficulty":1,"url":"/machines/groel#story","cites":[{"source":"fact:G8","machine":"groel","label":"Temperatures at which E. coli needs GroEL and GroES to grow: 17–42 °C","section":"story"},{"source":"fact:G7","machine":"groel","label":"E. coli proteins that bind GroEL: 250 of about 2,400 cytosolic proteins","section":"story"},{"source":"ref:fayet1989","machine":"groel","label":"Fayet 1989","section":"sources","href":"https://doi.org/10.1128/jb.171.3.1379-1385.1989"},{"source":"ref:kerner2005","machine":"groel","label":"Kerner et al.","section":"sources","anchor":"ref-kerner2005","href":"https://doi.org/10.1016/j.cell.2005.05.028"}]},{"id":"groel-human-hsp60","machine":"groel","kind":"qa","prompt":"What is the GroEL relative in human mitochondria called?","answer":"Hsp60","explanation":"Mitochondria descend from bacteria and kept this folding chamber. Human Hsp60 with its lid, Hsp10, lets E. coli grow without its own GroEL and GroES.","section":"story","topic":"parts","sources":["fact:G9","ref:cheng1989","ref:hansen2002"],"tags":["mitochondria","evolution"],"difficulty":1,"url":"/machines/groel#story","cites":[{"source":"fact:G9","machine":"groel","label":"Human relative of GroEL: Hsp60 in mitochondria","section":"story"},{"source":"ref:cheng1989","machine":"groel","label":"Cheng 1989","section":"sources","href":"https://doi.org/10.1038/337620a0"},{"source":"ref:hansen2002","machine":"groel","label":"Hansen 2002","section":"sources","href":"https://doi.org/10.1086/339935"}]},{"id":"groel-quiet-room-open-question","machine":"groel","kind":"qa","prompt":"The GroEL chamber is often pictured as \"a quiet room for one\". What does that picture leave open?","answer":"Whether the chamber actively helps the fold, beyond keeping other chains out.","explanation":"This is debated (Hayer-Hartl et al. 2016; Horwich et al. 2009). The room also changes: its walls are sticky while catching the chain and water-loving once the lid closes.","section":"story","topic":"debate","sources":["analogy:A quiet room for one","ref:hayerhartl2016","ref:horwich2009"],"tags":["analogy","debate"],"difficulty":3,"url":"/machines/groel#story","cites":[{"source":"analogy:A quiet room for one","machine":"groel","label":"Analogy: A quiet room for one","section":"story"},{"source":"ref:hayerhartl2016","machine":"groel","label":"Hayer-Hartl et al.","section":"sources","anchor":"ref-hayerhartl2016","href":"https://doi.org/10.1016/j.tibs.2015.07.009"},{"source":"ref:horwich2009","machine":"groel","label":"Horwich et al.","section":"sources","anchor":"ref-horwich2009","href":"https://doi.org/10.1017/s0033583509004764"}]},{"id":"groel-second-chance-by-chance","machine":"groel","kind":"qa","prompt":"How does a chain that GroEL releases still unfolded get another round of folding?","answer":"It simply binds GroEL again by chance; GroEL does not check the result.","explanation":"Of about 300 new proteins that bind GroEL strongly, about one third are unstable and return to it again and again.","section":"story","topic":"cycle","sources":["analogy:A second chance","fact:G6","ref:houry1999"],"tags":["analogy","rebinding"],"difficulty":2,"url":"/machines/groel#story","cites":[{"source":"analogy:A second chance","machine":"groel","label":"Analogy: A second chance","section":"story"},{"source":"fact:G6","machine":"groel","label":"New proteins that bind GroEL strongly: 300 proteins","section":"story"},{"source":"ref:houry1999","machine":"groel","label":"Houry 1999","section":"sources","href":"https://doi.org/10.1038/45977"}]},{"id":"groel-size-limit-method","machine":"groel","kind":"qa","prompt":"How did Sakikawa and colleagues (1999) find which unfolded E. coli proteins fit inside the closed GroEL–GroES cage?","answer":"They closed GroES over the captured proteins and digested everything outside with protease; only proteins inside survived.","explanation":"Only proteins smaller than one 57 kDa GroEL subunit survived. An 82 kDa GFP trimer bound GroEL but was always digested, so it never entered.","section":"evidence","topic":"numbers","sources":["evidence:cis-cavity-size-limit","evidence:gfp-trimer-excluded","ref:sakikawa1999"],"tags":["method","size"],"difficulty":2,"url":"/machines/groel#evidence","cites":[{"source":"evidence:cis-cavity-size-limit","machine":"groel","label":"Largest protein held in the closed cis cavity (Sakikawa C 1999)","section":"evidence","anchor":"ev-cis-cavity-size-limit"},{"source":"evidence:gfp-trimer-excluded","machine":"groel","label":"Fate of an 82-kDa protein at GroEL-GroES (Sakikawa C 1999)","section":"evidence","anchor":"ev-gfp-trimer-excluded"},{"source":"ref:sakikawa1999","machine":"groel","label":"Sakikawa et al.","section":"sources","anchor":"ref-sakikawa1999","href":"https://doi.org/10.1074/jbc.274.30.21251"}]},{"id":"groel-hydrolysis-rates-differ","machine":"groel","kind":"qa","prompt":"ATP hydrolysis in the closed GroEL ring was measured at 0.12 s^-1 per subunit (Burston et al. 1995) and as a burst at 0.518 s^-1 (Ye and Lorimer 2013). Why do the two rates differ?","answer":"The studies used different methods and salt conditions.","explanation":"Burston and colleagues used transient kinetics after GroES binding; Ye and Lorimer followed phosphate release by stopped-flow at 0.2 M K+.","section":"evidence","topic":"debate","sources":["evidence:atp-hydrolysis-burst","evidence:atp-hydrolysis-in-cis-complex","stat:ATP hydrolysis rate","ref:ye2013","ref:burston1995"],"tags":["atp","kinetics"],"difficulty":3,"url":"/machines/groel#evidence","cites":[{"source":"evidence:atp-hydrolysis-burst","machine":"groel","label":"Pre-steady-state ATP hydrolysis and ADP release rates (Ye X 2013)","section":"evidence","anchor":"ev-atp-hydrolysis-burst"},{"source":"evidence:atp-hydrolysis-in-cis-complex","machine":"groel","label":"Rate of ATP hydrolysis in the GroEL-ATP7-GroES complex (Burston SG 1995)","section":"evidence","anchor":"ev-atp-hydrolysis-in-cis-complex"},{"source":"stat:ATP hydrolysis rate","machine":"groel","label":"Key number: ATP hydrolysis rate","section":"summary"},{"source":"ref:ye2013","machine":"groel","label":"Ye and Lorimer, PNAS 2013","section":"sources","href":"https://doi.org/10.1073/pnas.1317702110"},{"source":"ref:burston1995","machine":"groel","label":"Burston et al.","section":"sources","anchor":"ref-burston1995","href":"https://doi.org/10.1006/jmbi.1995.0285"}]},{"id":"groel-groes-stay-no-substrate","machine":"groel","kind":"qa","prompt":"Without substrate protein, about how long does the GroES lid stay on E. coli GroEL?","answer":"About 24 s.","explanation":"In trapping experiments GroES left at 0.042 s^-1 per subunit, the same as the steady-state ATPase rate; 24 s is 1 divided by that rate. Without substrate, GroES release is the slowest step.","section":"evidence","topic":"numbers","sources":["evidence:groes-release-steady-state","stat:GroES release rate","ref:burston1995"],"tags":["groes","kinetics"],"difficulty":2,"url":"/machines/groel#evidence","cites":[{"source":"evidence:groes-release-steady-state","machine":"groel","label":"GroES dissociation rate during steady-state cycling (Burston SG 1995)","section":"evidence","anchor":"ev-groes-release-steady-state"},{"source":"stat:GroES release rate","machine":"groel","label":"Key number: GroES release rate","section":"summary"},{"source":"ref:burston1995","machine":"groel","label":"Burston et al.","section":"sources","anchor":"ref-burston1995","href":"https://doi.org/10.1006/jmbi.1995.0285"}]},{"id":"groel-substrate-speeds-release","machine":"groel","kind":"cloze","prompt":"In stopped-flow FRET experiments, unfolded substrate protein sped up GroES release from GroEL {{20- to 50-fold}}.","answer":"20- to 50-fold","explanation":"The fast route grew with denatured Rubisco. Unfolded protein binds the open ring first and speeds release of the old cage, so GroEL spends its time folding rather than waiting.","section":"evidence","topic":"numbers","sources":["evidence:substrate-accelerates-groes-release","ref:rye1999"],"tags":["groes","kinetics","fret"],"difficulty":2,"url":"/machines/groel#evidence","cites":[{"source":"evidence:substrate-accelerates-groes-release","machine":"groel","label":"GroES release when non-native protein is present (Rye HS 1999)","section":"evidence","anchor":"ev-substrate-accelerates-groes-release"},{"source":"ref:rye1999","machine":"groel","label":"Rye et al.","section":"sources","anchor":"ref-rye1999","href":"https://doi.org/10.1016/s0092-8674(00)80742-4"}]},{"id":"groel-cage-volume-method","machine":"groel","kind":"qa","prompt":"How did Tang and colleagues (2006) change the volume of the GroEL cavity?","answer":"By deleting or extending the C-terminal Gly-Gly-Met repeats that hang into it.","explanation":"Shrinking the cavity by 1.9–4.4% sped folding of 33 kDa rhodanese and MetF, while any change slowed 41 kDa MBP and 50 kDa RuBisCo. The natural cage size suits fast folding, not just shelter.","section":"evidence","topic":"parts","sources":["evidence:cage-volume-sets-folding-speed","ref:tang2006"],"tags":["method","chamber"],"difficulty":3,"url":"/machines/groel#evidence","cites":[{"source":"evidence:cage-volume-sets-folding-speed","machine":"groel","label":"Effect of cavity volume on folding speed (Tang YC 2006)","section":"evidence","anchor":"ev-cage-volume-sets-folding-speed"},{"source":"ref:tang2006","machine":"groel","label":"Tang et al.","section":"sources","anchor":"ref-tang2006","href":"https://doi.org/10.1016/j.cell.2006.04.027"}]},{"id":"groel-sr1-folds-inside","machine":"groel","kind":"qa","prompt":"Rhodanese trapped under GroES in single-ring GroEL (SR1), which never opens, still became active. What does this show?","answer":"The protein folds inside the closed cage, not only after release.","explanation":"The trapped rhodanese reached native activity with a half-time of about 7 min while still bound to SR1.","section":"evidence","topic":"cycle","sources":["evidence:folding-inside-single-ring","ref:weissman1996"],"tags":["sr1","chamber"],"difficulty":2,"url":"/machines/groel#evidence","cites":[{"source":"evidence:folding-inside-single-ring","machine":"groel","label":"Folding inside a cage that never opens (Weissman JS 1996)","section":"evidence","anchor":"ev-folding-inside-single-ring"},{"source":"ref:weissman1996","machine":"groel","label":"Weissman et al.","section":"sources","anchor":"ref-weissman1996","href":"https://doi.org/10.1016/s0092-8674(00)81293-3"}]},{"id":"groel-one-or-two-lids-in-cells","machine":"groel","kind":"cloze","prompt":"In living E. coli cells, {{55 to 70%}} of GroEL carried one GroES lid and the rest carried two.","answer":"55 to 70%","explanation":"With client protein in vitro, Ye and Lorimer found most complexes carry GroES on both rings (\"footballs\"), so the simple one-lid alternating cycle is not the whole story.","section":"evidence","topic":"debate","sources":["step:The other ring takes its turn","ref:wagner2024","ref:ye2013"],"tags":["football","in-cell"],"difficulty":3,"url":"/machines/groel#evidence","cites":[{"source":"step:The other ring takes its turn","machine":"groel","label":"Step: The other ring takes its turn","section":"mechanism"},{"source":"ref:wagner2024","machine":"groel","label":"Wagner et al.","section":"sources","href":"https://doi.org/10.1038/s41586-024-07843-w"},{"source":"ref:ye2013","machine":"groel","label":"Ye and Lorimer, PNAS 2013","section":"sources","href":"https://doi.org/10.1073/pnas.1317702110"}]}]}