PURIFICATION OF A CALCIUM-BINDING PROTEIN (RAT SPARC) FROM PRIMARY SERTOLI CELL-ENRICHED CULTURE-MEDIUM

A protein with an apparent Mr of 43,000 was purified from Sertoli cell-enriched culture medium by sequential anion-exchange, gel permeation, C4 reversed-phase, and diphenyl reversed-phase HPLC. N-Terminal sequence analysis of this protein revealed a sequence of NH2-XPQTEAAEEMVAEETVV for the first 17 amino acids. Comparison of this sequence with existing protein data base maintained at the Protein Identification Resource revealed that it shares extensive identity with a previously described protein secreted by mouse embryo parietal endoderm, SPARC, which is equivalent to a protein secreted by a basement-membrane-producing tumor, BM-40; and a bone protein, osteonectin. This protein also possesses similar in vitro biological activity of SPARC in which it binds Ca2+. The possible physiological significance of this protein was discussed. © 1990.