Question

A protein (such as DnaK in E. coli) that binds to new polypeptides while they are still on ribosomes. Recognizes hydrophobic residues on pps, keeps the pp from binding to anything, keeps the peptide unfolded until productive folding interactions can occur. Consists of two domains: an N-terminal ATP-binding domain and a central domain that binds peptides with exposed hydrophobic regions.

A) GroEL
B) Hsp70
C) DnaJ
D) Hsp90

Answer 1

The protein described is Hsp70, which is a chaperone protein that binds to new polypeptides to prevent premature folding or interactions and assist with correct protein folding. In E. coli, DnaK is an example of Hsp70, which has both an N-terminal ATP-binding domain and a peptide-binding domain.

Step-by-step explanation:

A protein that fulfills the described functions—binding to new polypeptides on ribosomes, recognizing hydrophobic residues, and preventing premature folding or interactions—is Hsp70. This type of protein assists in the correct folding of newly synthesized proteins by temporarily stabilizing them in an unfolded state. Hsp70 proteins have an N-terminal ATP-binding domain and a peptide-binding domain that interacts with hydrophobic regions of polypeptides. This effectively keeps the polypeptide chain in an extended conformation until it can fold properly into its functional three-dimensional shape, thus preventing misfolding or aggregation.

In E. coli, DnaK is a well-known example of an Hsp70 chaperone. This molecular chaperone collaborates with other proteins like DnaJ (a co-chaperone) and GrpE (a nucleotide exchange factor) to facilitate protein folding and maintain proteostasis within the cell. The correct answer to the student's question is B) Hsp70.