PDBsum entry 3wms

Transferase

PDB id: 3wms

Contents

Protein chain

685 a.a.

Metals

_CA ×2

Waters ×270

References listed in PDB file

Key reference

• Title: Structural basis of a mutant y195i α-Cyclodextrin glycosyltransferase with switched product specificity from α-Cyclodextrin to β-/γ-Cyclodextrin.
• Authors: T.Xie, Y.Hou, D.Li, Y.Yue, S.Qian, Y.Chao.
• Ref.: J Biotechnol, 2014, 182, 92-96. [DOI no: 10.1016/j.jbiotec.2014.03.014]
• PubMed id: 24637377

Abstract

Cyclodextrin glycosyltransferase (EC 2.4.1.19) (CGTase) is an extracellular bacterial enzyme which has the unique capability of forming cyclodextrins from starch. Our previous investigation revealed that a mutant Y195I α-CGTase drastically altered the cyclodextrin specificity by switching toward the synthesis of both β- and γ-CDs (Xie et al., 2013a,b). In this study, we determined one X-ray structure of the mutant Y195I α-CGTase at 2.3Å. The overall structure was similar to that of the typical β-CGTase from Bacillus circulans 251, with minor difference in flexible domains since they showed about 70% homogeneity of amino acid sequences. The central site with isoleucine tended to be more flexible than tyrosine thus made the sugar chain, during the cyclization process, form a larger cyclodextrin like β- and γ-CDs surrounding the central site instead of α-CD. Superposition of the structure of Y195I α-CGTase with those of β-CGTase and γ-CGTase showed that residues Lys232, Lys89 and Arg177 at subsites +2, -3 and -7 could form smaller substrate binding cavity. In summary, the crystal structure revealed that moderate increase of mobility of the central site resulted in the switched product specificity from α-CD to β- and γ-CDs of the mutant Y195I α-CGTase. The space differences alongside the active domain may be another factor that impacts the product specificity of the CGTase.