IDENTIFICATION OF PROTEIN-C IN SERA OF THE FROGS, RANA-NIGROMACULATA AND RANA-BREVIPODA

When sera from the frogs, Rana (R.) nigromaculata and Rana (R.) brevip oda, were run on starch-gel electrophoresis (SGE), several bands were seen in an electrophoretic pattern of proteins. This pattern on SGE ap peared the same at stages XIV, XV and XXI, and in the adult frog, R. n iguromaculata. However, the pattern at stage X was different. A protei n, designated ''protein C'', did not appear clearly at this stage, but afterwards. This protein was the second richest among serum proteins of mature frogs. Protein C (Mr=180 kD, when estimated by SDS-PAGE) was obtained after SGE and then subjected to an NH2-terminal sequence ana lysis. Sequences of protein C from R. nigromaculata and R. brevipoda w ere NH2-TDPMYVIFIPQTLXE for the first 15 amino acids and NH2-TDPHYVIFK G for the first 10 amino acids, respectively. Homology search of GenBa nk sequences indicated no significant similarity with any known protei ns. The results suggest that protein C is a new protein, and that it m ay play an important role(s) in the serum after stage X in these speci es.