2Scientific Center of Russian Federation Research Institute for Genetics and Selection of Industrial Microorganisms, 1-yi Dorozhnyi Proezd 1, 117545 Moscow, Russia; fax: (495) 315-0501; E-mail: email@example.com
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Received October 15, 2012; Revision received November 9, 2012
The 3D structure of recombinant bacterial carboxypeptidase T (CPT) in complex with N-BOC-L-leucine was determined at 1.38 Å resolution. Crystals for the X-ray study were grown in microgravity using the counter-diffusion technique. N-BOC-L-leucine and SO42– ion bound in the enzyme active site were localized in the electron density map. Location of the leucine side chain in CPT–N-BOC-L-leucine complex allowed identification of the S1 subsite of the enzyme, and its structure was determined. Superposition of the structures of CPT–N-BOC-L-leucine complex and complexes of pancreatic carboxypeptidases A and B with substrate and inhibitors was carried out, and similarity of the S1 subsites in these three carboxypeptidases was revealed. It was found that SO42– ion occupies the same position in the S1′ subsite as the C-terminal carboxy group of the substrate.
KEY WORDS: carboxypeptidase T, S1 subsite, crystal structure, X-ray structural analysis