Krishnan R, Sadler J E, Tulinsky A
Department of Chemistry, Michigan State University, East Lansing, MI 48824, USA.
Acta Crystallogr D Biol Crystallogr. 2000 Apr;56(Pt 4):406-10. doi: 10.1107/s0907444900001487.
The Ser195Ala mutant of human alpha-thrombin was complexed with fibrinopeptide A(7-22) (FPA) in an effort to describe the (P1'-P6') post-cleavage binding subsites of the fibrinogen-recognition exosite and define more clearly the nature of the Michaelis complex and the scissile peptide bond bound at the catalytic site. The thrombin mutant, however, has residual catalytic activity and proteolysis occurred at the Arg16-Gly17 bond. Thus, the structure of the thrombin complex determined was that of FPA(7-16) bound at the active site, which is very similar to the ternary FPA(7-16)cmk-human thrombin-hirugen complex (r.m.s.d. approximately 0.4 A; Stubbs et al. , 1992). It is further shown by subsidiary experiments that the cleavage is the result of residual catalytic activity of the altered catalytic machinery.
为了描述纤维蛋白原识别外位点的（P1'-P6'）切割后结合亚位点，并更清楚地定义米氏复合物的性质以及结合在催化位点的可裂解肽键，将人α-凝血酶的Ser195Ala突变体与纤维蛋白肽A(7-22)（FPA）复合。然而，凝血酶突变体具有残余催化活性，并且在Arg16-Gly17键处发生了蛋白水解。因此，所确定的凝血酶复合物的结构是FPA(7-16)结合在活性位点，这与三元FPA(7-16)cmk-人凝血酶-水蛭素复合物非常相似（均方根偏差约为0.4 Å；斯塔布斯等人，1992年）。辅助实验进一步表明，切割是改变后的催化机制残余催化活性的结果。
