PDBsum entry: 1ogg

Hydrolase

PDB id: 1ogg

Contents

Protein chains

497 a.a. *

Ligands

NAA-NAA-AMI ×2

GOL ×6

SO4

Waters ×861

* Residue conservation analysis

PDB id:

1ogg

Name:

Hydrolase

Title:

Chitinase b from serratia marcescens mutant d142n in complex with inhibitor allosamidin

Structure:

Chitinase b. Chain: a, b. Engineered: yes. Mutation: yes

Source:

Serratia marcescens. Organism_taxid: 615. Strain: bjl200. Expressed in: escherichia coli. Expression_system_taxid: 562.

Biol. unit:

Dimer (from PDB file)

Resolution:

1.97Å R-factor: 0.198 R-free: 0.238

Authors:

G.Vaaje-Kolstad,D.R.Houston,F.V.Rao,M.G.Peter,B.Synstad, D.M.F.Van Aalten,V.G.H.Eijsink

Key ref:

G.Vaaje-Kolstad et al. (2004). Structure of the D142N mutant of the family 18 chitinase ChiB from Serratia marcescens and its complex with allosamidin. Biochim Biophys Acta, 1696, 103-111. PubMed id: 14726210

Date:

30-Apr-03 Release date: 27-Apr-04

Protein chains

P11797  (CHIB_SERMA) -  Chitinase B

Seq: 499 a.a.

Struc: 497 a.a.*

* PDB and UniProt seqs differ at 9 residue positions (black crosses)

Enzyme reactions

• Enzyme class: E.C.3.2.1.14 - Chitinase.
• Reaction: Hydrolysis of the 1,4-beta-linkages of N-acetyl-D-glucosamine polymers of chitin.

 Gene Ontology (GO) functional annotation 

• Cellular component: extracellular region (1 term)
• Biological process: carbohydrate metabolic process (2 terms)
• Biochemical function: catalytic activity (5 terms)

Biochim Biophys Acta 1696:103-111 (2004)

PubMed id: 14726210

Structure of the D142N mutant of the family 18 chitinase ChiB from Serratia marcescens and its complex with allosamidin.

G.Vaaje-Kolstad, D.R.Houston, F.V.Rao, M.G.Peter, B.Synstad, D.M.van Aalten, V.G.Eijsink.

ABSTRACT

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.