An aspartyl protease binds the N-terminus of a polypeptide by specifically bindi

Question

An aspartyl protease binds the N-terminus of a polypeptide by specifically binding its sequence: N-Met-Ala-Phe-Lys-Ala-Thr-...

a. How many positively charged groups on the protease would ideally be used in binding of the peptide substrate?

A) 0

B) 1

C) 2

D) 3

E) 4

b. How many negatively charged groups on the protease would ideally be used in binding and cleaving of the peptide substrate?

A) 0

B)1

C) 2

D) 3

E) 4

c.Asuming that an aromatic group can stack on both sides of its ring system, how many phenylalanines could potentially (and ideally) interact with the substrate?

A) 0

B) 1

C) 2

D) 3

E) 4

d .An ideal inhibitor (not a drug) designed based on the hexapeptide substrate of this protease would have a molecular weight between 600 and750 g/mol.

A) True

B) False

e.Phosphorylation of the threonine on the substrate would likely prevent cleavage by the protease.

A) True

B) False

Explanation / Answer

a. An aspartyl protease binds to polypeptide through specific signal sequence of N-Met-Ala-Phe-Lys-Ala-Thr-... In this sequence, Lysine (Lys) is the only positively chrged residue that can ideally be used in binding of the peptide substrate. The option B is correct.

b. Among the amino acids, negatively charged amino acids are aspartic acid and glutamic acid. The aspartyl protease do not contain these residues in its signal sequence. Therefore, option A is correct.

c. The signal sequence of aspartyl protease contains one phenylalanine residue that can iteract with substrate on both sides of its ring system. Therefore, option A is correct.

d. The given statement is false. This is because the aspartyl protease molecular weight must be known to design an ideal inhibitor that can effectively inhibit the enzyme. Option B is correct.

e. Phosphorylation of threonine on substrate at C - terminal may prevent the cleavage by protease. Therefore, it is true. Option A is correct.

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