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1eib

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[[Image:1eib.gif|left|200px]]
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{{STRUCTURE_1eib| PDB=1eib | SCENE= }}
{{STRUCTURE_1eib| PDB=1eib | SCENE= }}
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'''CRYSTAL STRUCTURE OF CHITINASE A MUTANT D313A COMPLEXED WITH OCTA-N-ACETYLCHITOOCTAOSE (NAG)8.'''
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===CRYSTAL STRUCTURE OF CHITINASE A MUTANT D313A COMPLEXED WITH OCTA-N-ACETYLCHITOOCTAOSE (NAG)8.===
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==Overview==
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Chitinase A (ChiA) from the bacterium Serratia marcescens is a hydrolytic enzyme, which cleaves beta-1,4-glycosidic bonds of the natural biopolymer chitin to generate di-N-acetyl-chitobiose. The refined structure of ChiA at 1.55 A shows that residue Asp313, which is located near the catalytic proton donor residue Glu315, is found in two alternative conformations of equal occupancy. In addition, the structures of the cocrystallized mutant proteins D313A, E315Q, Y390F, and D391A with octa- or hexa-N-acetyl-glucosamine have been refined at high resolution and the interactions with the substrate have been characterized. The obtained results clearly show that the active site is a semiclosed tunnel. Upon binding, the enzyme bends and rotates the substrate in the vicinity of the scissile bond. Furthermore, the enzyme imposes a critical "chair" to "boat" conformational change on the sugar residue bound to the -1 subsite. According to our results, we suggest that residues Asp313 and Tyr390 along with Glu315 play a central role in the catalysis. We propose that after the protonation of the substrate glycosidic bond, Asp313 that interacts with Asp311 flips to its alternative position where it interacts with Glu315 thus forcing the substrate acetamido group of -1 sugar to rotate around the C2-N2 bond. As a result of these structural changes, the water molecule that is hydrogen-bonded to Tyr390 and the NH of the acetamido group is displaced to a position that allows the completion of hydrolysis. The presented results suggest a mechanism for ChiA that modifies the earlier proposed "substrate assisted" catalysis.
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(as it appears on PubMed at http://www.pubmed.gov), where 11560481 is the PubMed ID number.
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{{ABSTRACT_PUBMED_11560481}}
==About this Structure==
==About this Structure==
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[[Category: Protein-oligosaccharide complex]]
[[Category: Protein-oligosaccharide complex]]
[[Category: Tim barrel]]
[[Category: Tim barrel]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 15:08:08 2008''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 1 00:44:37 2008''

Revision as of 21:44, 30 June 2008

Image:1eib.png

Template:STRUCTURE 1eib

CRYSTAL STRUCTURE OF CHITINASE A MUTANT D313A COMPLEXED WITH OCTA-N-ACETYLCHITOOCTAOSE (NAG)8.

Template:ABSTRACT PUBMED 11560481

About this Structure

1EIB is a Single protein structure of sequence from Serratia marcescens. Full crystallographic information is available from OCA.

Reference

High resolution structural analyses of mutant chitinase A complexes with substrates provide new insight into the mechanism of catalysis., Papanikolau Y, Prag G, Tavlas G, Vorgias CE, Oppenheim AB, Petratos K, Biochemistry. 2001 Sep 25;40(38):11338-43. PMID:11560481

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