循环芽孢杆菌
化学
麦芽糖
立体化学
结晶学
生物化学
酶
作者
Catherine L. Lawson,Rob van Montfort,B.V. Strokopytov,H.J. Rozeboom,Kor H. Kalk,G.E de Vries,Dirk Penninga,Lubbert Dijkhuizen,Bauke W. Dijkstra
标识
DOI:10.1006/jmbi.1994.1168
摘要
The cyclodextrin glycosyltransferase (CGTase, EC 2.4.1.19) gene from Bacillus circulans strain 251 was cloned and sequenced. It was found to code for a mature protein of 686 amino acid residues, showing 75% identity to the CGTase from B. circulans strain 8. The X-ray structure of the CGTase was elucidated in a maltodextrin-dependent crystal form and refined against X-ray diffraction data to 2·0 Å resolution. The structure of the enzyme is nearly identical to the CGTase from B. circulans strain 8. Three maltose binding sites are observed at the protein surface, two in domain E and one in domain C. The maltose-dependence of CGTase crystallization can be ascribed to the proximity of two of the maltose binding sites to intermolecular crystal contacts. The maltose molecules bound in the E domain interact with several residues implicated in a raw starch binding motif conserved among a diverse group of starch converting enzymes.
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