Bovine factor X1 (Stuart factor). Primary structure of the light chain.

The amino-acid sequence of the light chain of bovine factor X1 is presented. The sequence of 112 of the 140 residues was determined automatically on fragments produced by specific cleavage of arginyl, glutamyl, tryptophanyl, and asparaginyl-glycine bonds. The remainder was determined by conventional procedures. The amino-terminal sequence of the light chain is homologous with the amino-terminal region of bovine prothrombin and, like the latter, appears to contain several residues of a recently discovered unusual amino acid, lambda-carboxy-glutamic acid. The role of this amino acid in the calcium-binding ability of factor X and prothrombin is discussed.