Isolation and sequence of the cDNA for human protein S, a regulator of blood coagulation.

Abstract
Protein S is a cofactor of activated protein C; together they function as a regulator of blood coagulation. A human liver cDNA library constructed in bacteriophage .lambda.gt11 was screened with DNA fragments from a full-length bovine cDNA clone encoding protein S. Several cDNA clones were isolated and sequenced. The combined cDNA sequences encoded the mature protein and 15 residues of the leader sequence when compared to bovine protein S. Human protein S is a single-chain consisting of 635 amino acids with 82% homology to bovine protein S. After an NH2-terminal .gamma.-carboxyglutamic acid-containing region, there is a short region with thrombin-sensitive bond(s), followed by a region with four repeat sequences with that are homologous to the precursor of mouse epidermal growth factor. In contrast to the other vitamin K-dependent plasma proteins, the COOH-terminal portion of human protein S does not show any resemblance to serine proteases.