In each of the following cases, predict whether the pKa value of the first residue will be upshifted or downshifted relative to the typical pKa value (Table 2.1) based on the microenvironment. Briefly (in no more than 2-3 sentences) explain your reasoning. (a) A His residue adjacent to two Arg residues on the surface of a protein(b) A Cys residue adjacent to an Asp residue in the active site of an enzyme(c) A Lys residue buried in the hydrophobic core of a globular protein Glutamate(Glu, E)C÷0CH₂COCH₂CH₂COO--COO-mateE)TABLE 2.1 Typical pK values of ionizable groups in proteinsGroupTerminal a-carboxyl groupAspartic acidGlutamic acidHistidineTerminal a-amino groupCysteineTyrosineLysineArginineHAcid0-N+ H-S-N++-NN=CH+ H...HHHHH-НHHHHON-H1N-HHHBase2N₂-N-NBilH1--NFO-S-HHN-CHHHNH-0-N-HTypical pK*pK values depend on temperature, ionic strength, and the microenvironment of the ionizable3.14.16.08.08.310.910.812.5grouphistidine, and aspartic and glutamic acids in proteins. Two other groups inproteins—the terminal a-amino group and the terminal a-carboxylgroup—can be ionized, and typical pK values for these groups also areincluded in Table 2.1.Amino acids are often designated by either a three-letter abbreviation ofa one-letter symbol (Table 2.2). The abbreviations for amino acids are thefirst three letters of their names, except for asparagine (Asn), glutamine(Gln), isoleucine (Ile), and tryptophan (Trp). The symbols foracids are the first letters of their names (e.g., G for glycine and L for leucine);many aminoaZ-HHHomoseandversaacidstions tacids nhomosethat limiproteinstheir cycl2.2 PriPeProteins aamino acis called atwo aminThe equisynthesisrequires akineti

Answered: In each of the following cases, predict…

Biochemistry

9th Edition

ISBN:9781319114671

Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Chapter1: Biochemistry: An Evolving Science

Section: Chapter Questions

Problem 1P

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Related questions

Question

In each of the following cases, predict whether the pKa value of the first residue will be upshifted or downshifted relative to the typical pKa value (Table 2.1) based on the microenvironment. Briefly (in
no more than 2-3 sentences) explain your reasoning.
(a) A His residue adjacent to two Arg residues on the surface of a protein
(b) A Cys residue adjacent to an Asp residue in the active site of an enzyme
(c) A Lys residue buried in the hydrophobic core of a globular protein

Glutamate
(Glu, E)
C÷0
CH₂
CO
CH₂
CH₂
COO-
-COO-
mate
E)
TABLE 2.1 Typical pK values of ionizable groups in proteins
Group
Terminal a-carboxyl group
Aspartic acid
Glutamic acid
Histidine
Terminal a-amino group
Cysteine
Tyrosine
Lysine
Arginine
H
Acid
0
-N
+ H
-S
-N
+
+
-N
N=C
H
+ H
...
H
H
H
H
H
-Н
H
H
H
H
O
N-H
1
N-H
H
H
Base
2
N₂
-N
-N
Bil
H
1
-
-N
FO
-S-
H
H
N-C
H
H
H
N
H
-0-
N-H
Typical pK
*pK values depend on temperature, ionic strength, and the microenvironment of the ionizable
3.1
4.1
6.0
8.0
8.3
10.9
10.8
12.5
group
histidine, and aspartic and glutamic acids in proteins. Two other groups in
proteins—the terminal a-amino group and the terminal a-carboxyl
group—can be ionized, and typical pK values for these groups also are
included in Table 2.1.
Amino acids are often designated by either a three-letter abbreviation of
a one-letter symbol (Table 2.2). The abbreviations for amino acids are the
first three letters of their names, except for asparagine (Asn), glutamine
(Gln), isoleucine (Ile), and tryptophan (Trp). The symbols for
acids are the first letters of their names (e.g., G for glycine and L for leucine);
many amino
a
Z-H
H
Homose
and
versa
acids
tions t
acids n
homose
that limi
proteins
their cycl
2.2 Pri
Pe
Proteins a
amino ac
is called a
two amin
The equi
synthesis
requires a
kineti

Expert Solution

Step 1

The pKa of a protein refers to the pH at which half of the protein's acidic residues (such as Asp or Glu) are protonated (have a hydrogen ion (H+) attached) and half are deprotonated (don't have a hydrogen ion attached). The pKa value is an important parameter for understanding the acid-base properties of a protein and how it interacts with its environment. It can affect a protein's stability, activity, and interactions with other molecules.