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1n29

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{{STRUCTURE_1n29| PDB=1n29 | SCENE= }}
{{STRUCTURE_1n29| PDB=1n29 | SCENE= }}
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'''Crystal structure of the N1A mutant of human group IIA phospholipase A2'''
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===Crystal structure of the N1A mutant of human group IIA phospholipase A2===
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==Overview==
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The human group IIA secreted PLA(2) is a 14 kDa calcium-dependent extracellular enzyme that has been characterized as an acute phase protein with important antimicrobial activity and has been implicated in signal transduction. The selective binding of this enzyme to the phospholipid substrate interface plays a crucial role in its physiological function. To study interfacial binding in the absence of catalysis, one strategy is to produce structurally intact but catalytically inactive mutants. The active site mutants H48Q, H48N, and H48A had been prepared for the secreted PLA(2)s from bovine pancreas and bee venom and retained minimal catalytic activity while the H48Q mutant showed the maximum structural integrity. Preparation of the mutant H48Q of the human group IIA enzyme unexpectedly produced an enzyme that retained significant (2-4%) catalytic activity that was contrary to expectations in view of the accepted catalytic mechanism. In this paper it is established that the high residual activity of the H48Q mutant is genuine, not due to contamination, and can be seen under a variety of assay conditions including assays in the presence of Co(2+) and Ni(2+) in place of Ca(2+). The crystallization of the H48Q mutant, yielding diffraction data to a resolution of 1.5 A, allowed a comparison with the corresponding recombinant wild-type enzyme (N1A) that was also crystallized. This comparison revealed that all of the important features of the catalytic machinery were in place and the two structures were virtually superimposable. In particular, the catalytic calcium ion occupied an identical position in the active site of the two proteins, and the catalytic water molecule (w6) was clearly resolved in the H48Q mutant. We propose that a variation of the calcium-coordinated oxyanion ("two water") mechanism involving hydrogen bonding rather than the anticipated full proton transfer to the histidine will best explain the ability of an active site glutamine to allow significant catalytic activity.
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(as it appears on PubMed at http://www.pubmed.gov), where 12501175 is the PubMed ID number.
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{{ABSTRACT_PUBMED_12501175}}
==About this Structure==
==About this Structure==
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[[Category: Wood, S P.]]
[[Category: Wood, S P.]]
[[Category: Hydrolase]]
[[Category: Hydrolase]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 01:59:56 2008''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 29 04:49:35 2008''

Revision as of 01:49, 29 July 2008

Image:1n29.png

Template:STRUCTURE 1n29

Crystal structure of the N1A mutant of human group IIA phospholipase A2

Template:ABSTRACT PUBMED 12501175

About this Structure

1N29 is a Single protein structure of sequence from Homo sapiens. Full crystallographic information is available from OCA.

Reference

The crystal structure of the H48Q active site mutant of human group IIA secreted phospholipase A2 at 1.5 A resolution provides an insight into the catalytic mechanism., Edwards SH, Thompson D, Baker SF, Wood SP, Wilton DC, Biochemistry. 2002 Dec 31;41(52):15468-76. PMID:12501175

Page seeded by OCA on Tue Jul 29 04:49:35 2008

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