Question

2. A protease is an enzyme that catalyzes the hydrolysis of proteins. These usually have histidine (his) in the active site as well as arginine(arg). Below is a "ribbon" model of its structure. Asp1022 ser Gly133 His5 IP a. Look up his and arg and show the calculations for establishing the charge on these amino acids (within the protein) at pH 3 and 7. b. Label with arrows, on the above model the types of secondary structure within this protein. c. Outline and/or illustrate, with labels, one elongation cycle of translation that will add arg to the growing protein.

Answer 1

Answer a:)

Histidine has the following pKa values

The pK₁ = 1.82

The pK_R­ = 6

The pK₂ = 9.17

Arginine has following pKa values:

The pK₁ = 2.17

The pK_R­ = 12.48

The pK₂ = 9.04

At pH 3, Histidine becomes neutral due to the deprotonation of COOH group.

At pH 3, Arginine also gets -1 charge due to the deprotonation of COOH group.

At pH 7, Histidine gets -1 charge due to the deprotonation of COOH group and a side chain (R-N⁺).

At pH 7, Arginine still contains -1 charge because only COOH group can deprotonate in this pH.

Answer b:)

The following image contains the secondary structures.

Answer c:)

The following image contains the elongation cycle of arginine.

Arginine E PA Next amino acid Anticodon tRNA tRNA binds to matching codon որրորՈՈՈՈՈՈՈՈՈՈՈրրը: EPA Codon Domandonninnnitelma E PA mRNA shifted forward, Exposed a new codon mononiendom E PA nonmoonnoottinni non The polypeptide now links to the new amino acid.

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