1xgz

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[[Image:1xgz.gif|left|200px]]
[[Image:1xgz.gif|left|200px]]
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{{Structure
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<!--
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|PDB= 1xgz |SIZE=350|CAPTION= <scene name='initialview01'>1xgz</scene>, resolution 2.0&Aring;
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The line below this paragraph, containing "STRUCTURE_1xgz", creates the "Structure Box" on the page.
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|SITE=
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You may change the PDB parameter (which sets the PDB file loaded into the applet)
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|LIGAND= <scene name='pdbligand=CA:CALCIUM+ION'>CA</scene>, <scene name='pdbligand=NAG:N-ACETYL-D-GLUCOSAMINE'>NAG</scene>, <scene name='pdbligand=PCA:PYROGLUTAMIC+ACID'>PCA</scene>
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or the SCENE parameter (which sets the initial scene displayed when the page is loaded),
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|ACTIVITY= <span class='plainlinks'>[http://en.wikipedia.org/wiki/Alpha-amylase Alpha-amylase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.2.1.1 3.2.1.1] </span>
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or leave the SCENE parameter empty for the default display.
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|GENE=
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|DOMAIN=
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{{STRUCTURE_1xgz| PDB=1xgz | SCENE= }}
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|RELATEDENTRY=[[1xh0|1XH0]], [[1xh1|1XH1]], [[1xh2|1XH2]]
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|RESOURCES=<span class='plainlinks'>[http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=1xgz FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1xgz OCA], [http://www.ebi.ac.uk/pdbsum/1xgz PDBsum], [http://www.rcsb.org/pdb/explore.do?structureId=1xgz RCSB]</span>
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}}
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'''Structure of the N298S variant of human pancreatic alpha-amylase'''
'''Structure of the N298S variant of human pancreatic alpha-amylase'''
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[[Category: Racaza, A.]]
[[Category: Racaza, A.]]
[[Category: Withers, S G.]]
[[Category: Withers, S G.]]
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[[Category: acarbose]]
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[[Category: Acarbose]]
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[[Category: amylase]]
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[[Category: Amylase]]
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[[Category: chloride]]
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[[Category: Chloride]]
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[[Category: enzyme]]
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[[Category: Enzyme]]
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[[Category: inhibitor]]
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[[Category: Inhibitor]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 15:00:48 2008''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Mar 31 00:49:29 2008''
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Revision as of 12:00, 3 May 2008

Image:1xgz.gif

Template:STRUCTURE 1xgz

Structure of the N298S variant of human pancreatic alpha-amylase


Overview

The mechanism of allosteric activation of alpha-amylase by chloride has been studied through structural and kinetic experiments focusing on the chloride-dependent N298S variant of human pancreatic alpha-amylase (HPA) and a chloride-independent TAKA-amylase. Kinetic analysis of the HPA variant clearly demonstrates the pronounced activating effect of chloride ion binding on reaction rates and its effect on the pH-dependence of catalysis. Structural alterations observed in the N298S variant upon chloride ion binding suggest that the chloride ion plays a variety of roles that serve to promote catalysis. One of these is having a strong influence on the positioning of the acid/base catalyst residue E233. Absence of chloride ion results in multiple conformations for this residue and unexpected enzymatic products. Chloride ion and N298 also appear to stabilize a helical region of polypeptide chain from which projects the flexible substrate binding loop unique to chloride-dependent alpha-amylases. This structural feature also serves to properly orient the catalytically essential residue D300. Comparative analyses show that the chloride-independent alpha-amylases compensate for the absence of bound chloride by substituting a hydrophobic core, altering the manner in which substrate interactions are made and shifting the placement of N298. These evolutionary differences presumably arise in response to alternative operating environments or the advantage gained in a particular product profile. Attempts to engineer chloride-dependence into the chloride-independent TAKA-amylase point out the complexity of this system, and the fact that a multitude of factors play a role in binding chloride ion in the chloride-dependent alpha-amylases.

About this Structure

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

Reference

Structural and mechanistic studies of chloride induced activation of human pancreatic alpha-amylase., Maurus R, Begum A, Kuo HH, Racaza A, Numao S, Andersen C, Tams JW, Vind J, Overall CM, Withers SG, Brayer GD, Protein Sci. 2005 Mar;14(3):743-55. PMID:15722449 Page seeded by OCA on Sat May 3 15:00:48 2008

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