Proteins called molecular chaperones assist in the process of protein folding. One class of chaperones found in organisms from bacteria to mammals is heat shock protein 90 (Hsp90). All Hsp90...

Proteins called molecular chaperones  assist in the process of protein folding. One class of chaperones found in organisms from bacteria to mammals is heat shock protein 90 (Hsp90). All Hsp90 chaperones contain a 10 amino acid “signature sequence” that allows ready identification of these proteins in sequence databases. Two representations of this signature sequence are shown below.

(a) In this sequence, which amino acid residues are invariant (conserved across all species)?
(b) At which position(s) are amino acids limited to those with positively charged side chains? For each position, which amino acid is more commonly found?
(c) At which positions are substitutions restricted to amino acids with negatively charged side chains? For each position, which amino acid predominates?
(d) There is one position that can be any amino acid, although one amino acid appears much more often than any other. What position is this, and which amino acid appears most often?