Molecular Machines

GroEL–GroES

The 28 review prompts from the notes on GroEL–GroES. Answer each in your head, then reveal it. Your grade decides when the card comes back.

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Summary 8

Read this section: Summary, in the GroEL–GroES notes

  1. What does GroEL do for a protein that has not folded?

  2. Which GroEL domain binds ATP and holds the two rings together?

  3. Through which helices does the GroEL apical domain bind both the unfolded substrate and GroES?

  4. Why does the archaeal thermosome, a group II chaperonin, need no GroES lid?

  5. GroEL is a cylinder of two stacked rings, each made of blank subunits.

  6. The closed GroEL–GroES chamber can hold unfolded proteins up to about blank.

  7. How many ATP does one GroEL ring bind and hydrolyse in each folding cycle?

  8. What did GroEL/GroES variants evolved to fold green fluorescent protein lose in return?

How it works 7

Read this section: How it works, in the GroEL–GroES notes

  1. What does an unfolded protein expose that lets the open GroEL ring catch it?

  2. In GroEL, ATP binding is cooperative within a ring but blank between the two rings.

  3. As the GroEL apical domains rise after ATP binds, they stretch the bound protein, which can blank.

  4. In GroEL, what makes the closed chamber on one ring open and release GroES?

  5. When GroES docks on GroEL, what does the final twist of about 100° of the apical domains do to the bound client?

  6. Why can a protein folding inside the closed GroEL chamber not aggregate?

  7. In GroEL, blank in the closed ring sets how long the chamber stays shut.

Big picture 6

Read this section: Big picture, in the GroEL–GroES notes

  1. In E. coli, why is a new protein chain that gets stuck half-folded a problem for the cell?

  2. In E. coli during normal growth, about blank of cytoplasmic protein passes through GroEL.

  3. How well does E. coli grow without GroEL and GroES?

  4. What is the GroEL relative in human mitochondria called?

  5. The GroEL chamber is often pictured as "a quiet room for one". What does that picture leave open?

  6. How does a chain that GroEL releases still unfolded get another round of folding?

Evidence 7

Read this section: Evidence, in the GroEL–GroES notes

  1. How did Sakikawa and colleagues (1999) find which unfolded E. coli proteins fit inside the closed GroEL–GroES cage?

  2. 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?

  3. Without substrate protein, about how long does the GroES lid stay on E. coli GroEL?

  4. In stopped-flow FRET experiments, unfolded substrate protein sped up GroES release from GroEL blank.

  5. How did Tang and colleagues (2006) change the volume of the GroEL cavity?

  6. Rhodanese trapped under GroES in single-ring GroEL (SR1), which never opens, still became active. What does this show?

  7. In living E. coli cells, blank of GroEL carried one GroES lid and the rest carried two.

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