Molecular cloning of a new erythropoiesis-stimulating activity (ESA36) from Streptomyces thermoviolaceus and expression in Escherichia coli.

Previous studies have shown that an Actinomycetes strain produces a novel protein with a molecular weight of 87,000 which stimulated the growth of murine erythroid progenitors in vitro, and we purified the protein. In this study, we have isolated and sequenced a clone encoding a polypeptide which had the equivalent activity. The clone contained an open reading frame of 334 amino acids. The activity was confirmed by the expression in E. coli as a fusion protein with glutathion S-transferase (GST). Based on the differences of molecular weight and N-terminal amino acid sequences, this protein was considered to be different from that previously reported and was named "ESA36".