A complementary DNA (cDNA) library was prepared from messenger RNA (mRNA) isolated from Syrian hamster islets. Bacterial colonies containing hamster preproinsulin cDNA were identified by cross-hybridization with the human preproinsulin gene. The sequences of two of these established the complete sequence of Syrian hamster preproinsulin mRNA and predicted the sequence of the protein. Hamster preproinsulin is 110 amino acids and possesses 90.0% and 82.7% identity with the corresponding proteins of rats (either I or II) and human beings, respectively. Analysis of the hybridization of hamster preproinsulin cDNA to restriction endonuclease digests of hamster DNA suggests that there is only a single preproinsulin gene in this rodent, in contrast to rats and mice, which possess two nonallelic genes.

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