Identification of candidate residues for interaction of protein S with C4b binding protein and activated protein C.
Protein S is a plasma factor essential for prevention of thrombosis, partly due to its activity as a cofactor for the plasma anticoagulant protease-activated protein C. To expand knowledge about structure-function relationships in homologous protein S molecules, studies of protein S from different species have been performed. Protein S anti-coagulant activity in human, monkey, bovine, and porcine plasma has been inactivated by purified human C4b binding protein (C4BP) with dose-dependence, suggesting that each protein S can bind human C4BP and that only the free form of each is anti-coagulantly active. Purified porcine protein S has a 10-fold higher Kd for human C4BP than has human protein S. Protein S residues 420-434 provide an essential binding site for the negative regulator C4BP. cDNA sequences show that protein S residues 420-434 are highly conserved in all four species with the notable exception of Lys-429-Ile in porcine protein S. Differences between porcine and human protein S, e.g. Lys-429-Ile, Lys-43-Ala, Ser-197-Leu, Ser 199-Phe, Glu-463-Gly, Lys-571-Glu, Asn-602-Ile, Gln-607-Pro, may contribute to the decreased affinity of porcine protein S for human C4BP. Moreover, the species specificity of cofactor activities of various species of protein S is determined for human versus bovine-activated protein C, and these results, combined with sequence comparisons, agree with previous evidence that the thrombin-sensitive region and the first epidermal growth factor domain of protein S, i.e. residues 47-116, are responsible for recognition of activated protein C.
Greengard
J S
JS
Department of Molecular and Experimental Medicine, Scripps Research Institute, La Jolla, CA 92037.
Fernandez
J A
JA
Radtke
K P
KP
Griffin
J H
JH
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002417:Cattle; D003001:Cloning, Molecular; D015935:Complement C4b / Q000378:metabolism; D017124:Conserved Sequence; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D015151:Immunoblotting; D008253:Macaca mulatta / Q000235:genetics*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D011486:Protein C / Q000378:metabolism; D017293:Protein S / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013329:Structure-Activity Relationship; D013552:Swine / Q000235:genetics*
D011486:Protein C; D017293:Protein S; D015935:Complement C4b