sr-Sturgeon Polypeptide-5 is a single chain recombinant protein produced by fermentation in Pichia pastoris. The starting gene is synthesized to be identical to the gene which codes for Kit Ligand derived from the sturgeon, Acipenser schrenckii. The parent protein contains a maximum of 315 amino acids which may contain disulfide bonds and/or glycosylation and consists of the proper sequence of the 20 standard amino acids.