期刊
JOURNAL OF BIOCHEMISTRY
卷 127, 期 4, 页码 635-643出版社
JAPANESE BIOCHEMICAL SOC
DOI: 10.1093/oxfordjournals.jbchem.a022651
关键词
cathepsin B; CA074; X-ray crystal structure; tertiary structure; substrate specificity; binding mode
The crystal structure of the bovine spleen cathepsin B (BSCB)-CAO74 complex was refined to R = 0.152 using X-ray diffraction data up to 2.18 Angstrom resolution. BSCB is characterized by an extra Cys148-Cys252 disulfide bridge, as compared with rat and human CBs. Although the crystal structures of these enzymes showed similar overall folding, a difference was observed in the occluding loop, a structural element specific only to CB, Comparison of the torsion angles indicated the different flexibilities of their loop structures. The oxirane C6 atom of CA074 was covalently bonded to the Cys29 S-gamma atom (C3-S-gamma=1.81 Angstrom), where the S-configuration was transformed to the R-form, Concerning the oxirane carbon atom that participates in the covalent bonding with the Cys residue, an acceptable rule has been proposed. The substrate specificities at the Sn (n = 1-3) and Sn' (n=1 and 2) subsites of CB, together with the interaction features as to CA074, have been discussed in comparison with the crystal structure of the papain-CA028 (a CA074-related inhibitor) complex.
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