Structural and functional analysis of substrate recognition by the 250s loop in amylomaltase from Thermus brockianus

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Title
Structural and functional analysis of substrate recognition by the 250s loop in amylomaltase from Thermus brockianus
Author(s)
J H Jung; Tae Yang Jung; D H Seo; S M Yoon; H C Choi; Byoung Chul Park; C S Park; Eui-Jeon Woo
Bibliographic Citation
Proteins-Structure Function and Bioinformatics, vol. 79, no. 2, pp. 633-644
Publication Year
2011
Abstract
Amylomaltase, or 4-α-glucanotransferase (EC 2.4.1.25), is involved in glycogen and maltooligosaccharide metabolism in microorganisms, catalyzing both the hydrolysis and transfer of an α-1,4-oligosacchraride to other sugar molecules. In this study, we determined the crystal structure of amylomaltase from Thermus brockianus at a resolution of 2.3 A and conducted a biochemical study to understand the detailed mechanism for its activity. Careful comparison with previous amylomaltase structures showed a pattern of conformational flexibility in the 250s loop with higher B-factor. Amylomaltase from T. brockianus exhibited a high transglycosylation factor for glucose and a lower value for maltose. Mutation of Gln256 resulted in increased Km for maltotriose and a sharp decrease of the transglycosylation factor for maltose, suggesting the involvement of Gln 256 in substrate binding between subsites +1 and +2. Mutation of Phe251 resulted in significantly lower glucose production but increased maltose production from maltopentose substrates, showing an altered substrate-binding affinity. The mutational data suggest the conformational flexibility of the loop may be involved in substrate binding in the GH77 family. Here, we present an action model of the 250s loop providing the molecular basis for the involvement of residues Phe251, Gln256, and Trp258 in the hydrolysis and transglycosylation activities in amylomaltase.
Keyword
250s loopAmylomaltaseSubstrate binding sitesThermus brockianus
ISSN
0887-3585
Publisher
Wiley
DOI
http://dx.doi.org/10.1002/prot.22911
Type
Article
Appears in Collections:
Critical Diseases Diagnostics Convergence Research Center > 1. Journal Articles
Division of Biomedical Research > Disease Target Structure Research Center > 1. Journal Articles
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