Crystal structures of Vibrio harveyi chitinase A complexed with chitooligosaccharides: Implications for the catalytic mechanism

Chomphunuch Songsiriritthigul, Supansa Pantoom, Adeleke H. Aguda, Robert C. Robinson, Wipa Suginta

Research output: Contribution to journalArticle

46 Citations (Scopus)

Abstract

This research describes four X-ray structures of Vibrio harveyi chitinase A and its catalytically inactive mutant (E315M) in the presence and absence of substrates. The overall structure of chitinase A is that of a typical family-18 glycosyl hydrolase comprising three distinct domains: (i) the amino-terminal chitin-binding domain; (ii) the main catalytic (α/β)8 TIM-barrel domain; and (iii) the small (α + β) insertion domain. The catalytic cleft of chitinase A has a long, deep groove, which contains six chitooligosaccharide ring-binding subsites (-4)(-3)(-2)(-1)(+1)(+2). The binding cleft of the ligand-free E315M is partially blocked by the C-terminal (His)6-tag. Structures of E315M-chitooligosaccharide complexes display a linear conformation of pentaNAG, but a bent conformation of hexaNAG. Analysis of the final 2Fo - Fc omit map of E315M-NAG6 reveals the existence of the linear conformation of the hexaNAG at a lower occupancy with respect to the bent conformation. These crystallographic data provide evidence that the interacting sugars undergo conformational changes prior to hydrolysis by the wild-type enzyme.

Original languageEnglish
Pages (from-to)491-499
Number of pages9
JournalJournal of Structural Biology
Volume162
Issue number3
DOIs
Publication statusPublished - Jun 1 2008
Externally publishedYes

Keywords

  • Chitin oligosaccharide
  • Chitinase
  • Crystal structure
  • The slide-and-bend mechanism
  • Vibrio harveyi

ASJC Scopus subject areas

  • Structural Biology

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