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Isolation of key amino acid residues at the N-terminal end of the core region Streptococcus downei glucansucrase, GTF-I

Lookup NU author(s): Dr Vincent Monchois, Emeritus Professor Roy Russell

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Abstract

Related streptococcal and Leuconostoc mesenteroides glucansucrases are enzymes of medical and biotechnological interest. Molecular modelling has suggested that the catalytic domain contains a circularly permuted version of the (β/α)8 barrel structure found in the amylase superfamily, and site- directed mutagenesis has identified critical amino acids in this region. In this study, sequential N-terminal truncations of Streptococcus downei GTF-I showed that key amino acids are also present in the first one-third of the core domain. Mutations were introduced at Trp-344, Glu-349 and His-355, residues that are conserved in all glucansucrases and lie within a region which is a target for inhibitory antibodies. W344L, E349L and H355V substitutions were assayed for their effect on mutant synthesis and also on oligosaccharide synthesis with various acceptors. It appeared that Trp-344 and His-355 are involved in the action mechanism of GTF-I; His-355 may also play a role in a binding subsite necessary for oligosaccharide and glucan elongation.

Publication metadata

Author(s): Monchois V; Russell RRB; Vignon M

Publication type: Article

Publication status: Published

Journal: Applied Microbiology and Biotechnology

Year: 1999

Volume: 52

Issue: 5

Pages: 660-665

Print publication date: 03/11/1999

ISSN (print): 0175-7598

ISSN (electronic): 1432-0614

Publisher: Springer

URL: http://dx.doi.org/10.1007/s002530051575

DOI: 10.1007/s002530051575

PubMed id: 10570812

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