Download MendeleyMolecular engineering of cycloisomaltooligosaccharide glucanotransferase from Bacillus circulans T-3040: structural determinants for the reaction product size and reactivity.
Suzuki, R., Suzuki, N., Fujimoto, Z., Momma, M., Kimura, K., Kitamura, S., Kimura, A., Funane, K.(2015) Biochem J 467: 259-270
- PubMed: 25649478 Search on PubMed
- DOI: https://doi.org/10.1042/BJ20140860
- Primary Citation Related Structures:
3WNP - PubMed Abstract:
Cycloisomaltooligosaccharide glucanotransferase (CITase) is a member of glycoside hydrolase family 66 and it produces cycloisomaltooligosaccharides (CIs). Small CIs (CI-7-9) and large CIs (CI-≥10) are designated as oligosaccharide-type CIs (oligo-CIs) and megalosaccharide-type CIs (megalo-CIs) respectively. CITase from Bacillus circulans T-3040 (BcCITase) produces mainly CI-8 with little megalo-CIs. It has two family 35 carbohydrate-binding modules (BcCBM35-1 and BcCBM35-2). BcCBM35-1 is inserted in a catalytic domain of BcCITase and BcCBM35-2 is located at the C-terminal region. Our previous studies suggested that BcCBM35-1 has two substrate-binding sites (B-1 and B-2) [Suzuki et al. (2014) J. Biol. Chem. 289, 12040-12051]. We implemented site-directed mutagenesis of BcCITase to explore the preference for product size on the basis of the 3D structure of BcCITase. Mutational studies provided evidence that B-1 and B-2 contribute to recruiting substrate and maintaining product size respectively. A mutant (mutant-R) with four mutations (F268V, D469Y, A513V and Y515S) produced three times as much megalo-CIs (CI-10-12) and 1.5 times as much total CIs (CI-7-12) as compared with the wild-type (WT) BcCITase. The 3D structure of the substrate-enzyme complex of mutant-R suggested that the modified product size specificity was attributable to the construction of novel substrate-binding sites in the B-2 site of BcCBM35-1 and reactivity was improved by mutation on subsite -3 on the catalytic domain.
- *Applied Microbiology Division, National Food Research Institute, National Agriculture and Food Research Organization, 2-1-12 Kannondai, Tsukuba 305-8642, Japan.
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