(c2) Identify the active site residues that make hydrogen bonds and electrostatic interac- tions with the oxygen atoms of the carboxylate groups of maleate in the diagram above. Identify the carboxylate groups according to the numbering in the diagram of maleate above. Indicate the hydrogen donor groups of the active site residues. (C3) Compare and draw the structures of L-Arg and L-Lys. On the basis of the diagram why does replacement of an arginine for a lysine have an effect on substrate binding to AspAT? (c4) Of the mutant enzymes in the table above, substitution of Arg292 by lysine is always asso- ciated with greatly weakened binding affinity of the substrate and decreased specificity. In the diagram above, examine the structural relationships between the two carboxylate groups of maleate with Arg- 292 and Arg386. Consider the change in binding relationships that maleate must undergo when Arg- 292 is mutated into a lysine in the AspAT(Lys292Arg386) enzyme and in the AspAT-(Lys292Lys386) enzyme. On the basis of the diagram above, describe the structural changes that must occur in each mutant giving rise to weaker substrate binding.

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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(c) On the right is a diagram of the ac
tive site of E. coli aspartate aminotrans-
ferase illustrating the cofactor pyridoxal
phosphate (labeled PLP) with the dicar-
boxylic acid maleate (labeled MAL)
bound in the active site. The structural
formula of maleate is shown on the right.
Am 194
MAL
Arg292
Arg386
Ilx17
Lauf
'coo-
H
get
H
Coo-
Maleate
(c1)
Draw the structure of L-aspartate and draw a border around the atoms in the amino
acid that maleate simulates.
(c2)
Identify the active site residues that make hydrogen bonds and electrostatic interac-
tions with the oxygen atoms of the carboxylate groups of maleate in the diagram above. Identify
the carboxylate groups according to the numbering in the diagram of maleate above. Indicate the
hydrogen donor groups of the active site residues.
(C3)
Compare and draw the structures of L-Arg and L-Lys. On the basis of the diagram
why does replacement of an arginine for a lysine have an effect on substrate binding to AspAT?
(c4)
Of the mutant enzymes in the table above, substitution of Arg292 by lysine is always asso-
ciated with greatly weakened binding affinity of the substrate and decreased specificity. In the diagram
above, examine the structural relationships between the two carboxylate groups of maleate with Arg-
292 and Arg386. Consider the change in binding relationships that maleate must undergo when Arg-
292 is mutated into a lysine in the AspAT(Lys292Arg386) enzyme and in the AspAT-(Lys292Lys386)
enzyme. On the basis of the diagram above, describe the structural changes that must occur in each
mutant giving rise to weaker substrate binding.
Transcribed Image Text:(c) On the right is a diagram of the ac tive site of E. coli aspartate aminotrans- ferase illustrating the cofactor pyridoxal phosphate (labeled PLP) with the dicar- boxylic acid maleate (labeled MAL) bound in the active site. The structural formula of maleate is shown on the right. Am 194 MAL Arg292 Arg386 Ilx17 Lauf 'coo- H get H Coo- Maleate (c1) Draw the structure of L-aspartate and draw a border around the atoms in the amino acid that maleate simulates. (c2) Identify the active site residues that make hydrogen bonds and electrostatic interac- tions with the oxygen atoms of the carboxylate groups of maleate in the diagram above. Identify the carboxylate groups according to the numbering in the diagram of maleate above. Indicate the hydrogen donor groups of the active site residues. (C3) Compare and draw the structures of L-Arg and L-Lys. On the basis of the diagram why does replacement of an arginine for a lysine have an effect on substrate binding to AspAT? (c4) Of the mutant enzymes in the table above, substitution of Arg292 by lysine is always asso- ciated with greatly weakened binding affinity of the substrate and decreased specificity. In the diagram above, examine the structural relationships between the two carboxylate groups of maleate with Arg- 292 and Arg386. Consider the change in binding relationships that maleate must undergo when Arg- 292 is mutated into a lysine in the AspAT(Lys292Arg386) enzyme and in the AspAT-(Lys292Lys386) enzyme. On the basis of the diagram above, describe the structural changes that must occur in each mutant giving rise to weaker substrate binding.
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