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Title
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Nucleotide sequence and X-ray structure of cyclodextrin glycosyltransferase from Bacillus circulans strain 251 in a maltose-dependent crystal form.
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Authors
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C.L.Lawson,
R.van Montfort,
B.Strokopytov,
H.J.Rozeboom,
K.H.Kalk,
G.E.de Vries,
D.Penninga,
L.Dijkhuizen,
B.W.Dijkstra.
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Ref.
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J Mol Biol, 1994,
236,
590-600.
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PubMed id
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Abstract
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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 A 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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