Download MendeleyStructural basis of a mutant Y195I alpha-cyclodextrin glycosyltransferase with switched product specificity from alpha-cyclodextrin to beta-/ gamma-cyclodextrin
Xie, T., Hou, Y.J., Li, D.F., Yue, Y., Qian, S.J., Chao, Y.P.(2014) J Biotechnol 182-183: 92-96
- PubMed: 24637377
- DOI: https://doi.org/10.1016/j.jbiotec.2014.03.014
- Primary Citation of Related Structures:
3WMS - PubMed 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.
Organizational Affiliation:
State Key Laboratories of Transducer Technology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China; CAS Key Laboratory of Microbial Physiological and Metabolic Engineering, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China.
