This old version of Proteopedia is provided for student assignments while the new version is undergoing repairs. Content and edits done in this old version of Proteopedia after March 1, 2026 will eventually be lost when it is retired in about June of 2026.

Apply for new accounts at the new Proteopedia. Your logins will work in both the old and new versions.


1g7x

From Proteopedia

(Difference between revisions)
Jump to: navigation, search
Line 1: Line 1:
-
[[Image:1g7x.gif|left|200px]]
+
{{Seed}}
 +
[[Image:1g7x.png|left|200px]]
<!--
<!--
Line 9: Line 10:
{{STRUCTURE_1g7x| PDB=1g7x | SCENE= }}
{{STRUCTURE_1g7x| PDB=1g7x | SCENE= }}
-
'''ASPARTATE AMINOTRANSFERASE ACTIVE SITE MUTANT N194A/R292L/R386L'''
+
===ASPARTATE AMINOTRANSFERASE ACTIVE SITE MUTANT N194A/R292L/R386L===
-
==Overview==
+
<!--
-
Systematic single and multiple replacement studies have been applied to Escherichia coli aspartate aminotransferase to probe the electrostatic effect of the two substrate-binding arginine residues, Arg292 and Arg386, and the structural effect of the pyridoxal 5'-phosphate-Asn194-Arg386 hydrogen-bond linkage system (PLP-N-R) on the pK(a) value of the Schiff base formed between pyridoxal 5'-phosphate (PLP) and Lys258. The electrostatic effects of the two arginine residues cannot be assessed by simple mutational studies of the residues. PLP-N-R lowers the pK(a) value of the PLP-Lys258 Schiff base by keeping it in the distorted conformation, which is unfavorable for protonation. Mutation of Arg386 eliminates its hydrogen bond with Asn194 and partially disrupts PLP-N-R, thereby relaxing the strain of the Schiff base. On the other hand, mutation of Arg292, the large domain residue that interacts with the small domain residue Asp15, makes the domain opening easier. Because PLP-N-R lies between the two domains, the domain opening increases the strain of the Schiff base. Therefore, the true electrostatic effects of Arg292 and Arg386 could be derived from mutational analysis of the enzyme in which PLP-N-R had been completely disrupted by the Asn194Ala mutation. Through the analyses, we could dissect the electrostatic and structural effects of the arginine mutations on the Schiff base pK(a). The positive charges of the two arginine residues and the PLP-N-R-mediated strain of the Schiff base lower the Schiff base pK(a) by 0.7 and 1.7, respectively. Thus, the electrostatic effect of the arginine residues is not as strong as has historically been thought, and this finding substantiates our recent finding that the imine-pyridine torsion of the Schiff base is the primary determinant (2.8 unit decrease) of the extremely low pK(a) value of the Schiff base [Hayashi, H., Mizuguchi, H., and Kagamiyama, H. (1998) Biochemistry 37, 15076-15085].
+
The line below this paragraph, {{ABSTRACT_PUBMED_11148029}}, adds the Publication Abstract to the page
 +
(as it appears on PubMed at http://www.pubmed.gov), where 11148029 is the PubMed ID number.
 +
-->
 +
{{ABSTRACT_PUBMED_11148029}}
==About this Structure==
==About this Structure==
Line 30: Line 34:
[[Category: Okada, K.]]
[[Category: Okada, K.]]
[[Category: Active site mutant]]
[[Category: Active site mutant]]
-
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 17:15:12 2008''
+
 
 +
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 1 04:51:08 2008''

Revision as of 01:51, 1 July 2008

Image:1g7x.png

Template:STRUCTURE 1g7x

ASPARTATE AMINOTRANSFERASE ACTIVE SITE MUTANT N194A/R292L/R386L

Template:ABSTRACT PUBMED 11148029

About this Structure

1G7X is a Single protein structure of sequence from Escherichia coli. Full crystallographic information is available from OCA.

Reference

Strain is more important than electrostatic interaction in controlling the pKa of the catalytic group in aspartate aminotransferase., Mizuguchi H, Hayashi H, Okada K, Miyahara I, Hirotsu K, Kagamiyama H, Biochemistry. 2001 Jan 16;40(2):353-60. PMID:11148029

Page seeded by OCA on Tue Jul 1 04:51:08 2008

Proteopedia Page Contributors and Editors (what is this?)

OCA

Retrieved from "http://52.214.119.220/wiki/index.php/1g7x"
Personal tools