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Crystal structures of carboxypeptidase T complexes with transition-state analogs
Recently, we have investigated the three-dimensional structures of CPT in complexes with the ground-state substrate analogs carrying hydrophobic and positively charged side chains: benzylsuccinic acid (BZS) and S-(2-guanidinoethylmercapto)succinic acid (GEMSA). That allowed us to identify Leu211 and Leu254 – earlier unknown determinants of substrate recognition by CPT as density of their interaction with substrates and localization of their side chains in the S1′-subsite were dependent on substrate’s structure. The role of Leu211 and Leu254 as structure determinants of hydrophobic selectivity of CPT was confirmed by site-directed mutagenesis. In the present work, we compare the structural organization of the CPT active site in complexes with transition state analogs of phenylalanine and arginine-containing substrates to evaluate structural basis of the enzyme’s catalytic activity to a broad range of substrates.