1ogb: Difference between revisions

Revision as of 03:48, 3 May 2008

CHITINASE B FROM SERRATIA MARCESCENS MUTANT D142N

OverviewOverview

Catalysis by ChiB, a family 18 chitinase from Serratia marcescens, involves a conformational change of Asp142 which is part of a characteristic D(140)XD(142)XE(144) sequence motif. In the free enzyme Asp142 points towards Asp140, whereas it rotates towards the catalytic acid, Glu144, upon ligand binding. Mutation of Asp142 to Asn reduced k(cat) and affinity for allosamidin, a competitive inhibitor. The X-ray structure of the D142N mutant showed that Asn142 points towards Glu144 in the absence of a ligand. The active site also showed other structural adjustments (Tyr10, Ser93) that had previously been observed in the wild-type enzyme upon substrate binding. The X-ray structure of a complex of D142N with allosamidin, a pseudotrisaccharide competitive inhibitor, was essentially identical to that of the wild-type enzyme in complex with the same compound. Thus, the reduced allosamidin affinity in the mutant is not caused by structural changes but solely by the loss of electrostatic interactions with Asp142. The importance of electrostatics was further confirmed by the pH dependence of catalysis and allosamidin inhibition. The pH-dependent apparent affinities for allosamidin were not correlated with k(cat), indicating that it is probably better to view the inhibitor as a mimic of the oxazolinium ion reaction intermediate than as a transition state analogue.

About this StructureAbout this Structure

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

ReferenceReference

Structure of the D142N mutant of the family 18 chitinase ChiB from Serratia marcescens and its complex with allosamidin., Vaaje-Kolstad G, Houston DR, Rao FV, Peter MG, Synstad B, van Aalten DM, Eijsink VG, Biochim Biophys Acta. 2004 Jan 14;1696(1):103-11. PMID:14726210 Page seeded by OCA on Sat May 3 03:48:33 2008

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OCA

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 '''CHITINASE B FROM SERRATIA MARCESCENS MUTANT D142N'''
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 [[Category: Synstad, B.]]
 [[Category: Vaaje-Kolstad, G.]]
-[[Category: chitin degradation]]
+[[Category: Chitin degradation]]
-[[Category: glycoside hydrolase]]
+[[Category: Glycoside hydrolase]]
-[[Category: hydrolase]]
+[[Category: Hydrolase]]
+''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May  3 03:48:33 2008''
-''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun Mar 30 22:44:52 2008''