1ali
From Proteopedia
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ALKALINE PHOSPHATASE MUTANT (H412N)
Overview
The X-ray structure of a mutant version of Escherichia coli alkaline, phosphatase (H412N) in which His-412 was replaced by Asn has been, determined at both low (-Zn) and high (+Zn) concentrations of zinc. In the, wild-type structure, His-412 is a direct ligand to one of the two, catalytically critical zinc atoms (Zn1) in the active site., Characterization of the H412N enzyme in solution revealed that the mutant, enzyme required high concentrations of zinc for maximal activity and for, high substrate and phosphate affinity (Ma L, Kantrowitz ER, 1994, J Biol, Chem 269:31614-31619). The H412N enzyme was also inhibited by Tris, in, contrast to the wild-type enzyme, which is activated more than twofold by, 1 M Tris. To understand these kinetic properties at the molecular level, the structure of the H412N (+Zn) enzyme was refined to an R-factor of, 0.174 at 2.2 A resolution, and the structure of the H412N(-Zn) enzyme was, refined to an R-factor of 0.166 at a resolution of 2.6 A. Both indicated, that the Asn residue substituted for His-412 did not coordinate well to, Zn1. In the H412N(-Zn) structure, the Zn1 site had very low occupancy and, the phosphate was shifted by 1.8 A from its position in the wild-type, structure. The Mg binding site was also affected by the substitution of, Asn for His-412. Both structures of the H412N enzyme also revealed a, surface-accessible cavity near the Zn1 site that may serve as a binding, site for Tris.(ABSTRACT TRUNCATED AT 250 WORDS)
About this Structure
1ALI is a Single protein structure of sequence from Escherichia coli with ZN, MG and PO4 as ligands. Active as Alkaline phosphatase, with EC number 3.1.3.1 Full crystallographic information is available from OCA.
Reference
Escherichia coli alkaline phosphatase: X-ray structural studies of a mutant enzyme (His-412-->Asn) at one of the catalytically important zinc binding sites., Ma L, Tibbitts TT, Kantrowitz ER, Protein Sci. 1995 Aug;4(8):1498-506. PMID:8520475
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