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Proc Natl Acad Sci U S A. 1989 Nov;86(21):8319-22.

Coagulation factor XII (Hageman factor) Washington D.C.: inactive factor XIIa results from Cys-571----Ser substitution.

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Department of Biology, Faculty of Science, Kyushu University, Fukuoka, Japan.


Structural studies on a congenital abnormal coagulation factor XII (Hageman factor), factor XII Washington D.C., have been performed to identify the defect responsible for its lack of procoagulant activity. Amino acid sequence analysis of a tryptic peptide isolated from the abnormal factor XII indicated that Cys-571 (equivalent to Cys-220 in the chymotrypsin numbering system) had been replaced by serine. No other substitutions in the active-site triad--namely, His-393, Asp-442, and Ser-544--were found. We propose that the Cys-571----Ser replacement found in this factor XII variant destroys the formation of the disulfide linkage between Cys-540 and Cys-571, giving rise to an altered conformation of the active-site serine residue or the secondary substrate-binding site and, thus, leads to the loss of enzyme activity.

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