The relationship of the bovine pituitary "diabetogenic peptide" to prolactin.

The bovine diabetogenic peptide (Louis) has been further purified by gel filtration. Material from the major protein peak was submitted to quantitative polyacrylamide gel electrophoresis. By the criteria of the joint 95 percent confidence envelope of KR and YO, related to molecular size and net charge, the diabetogenic peptide more closely resembles prolactin than growth hormone. By sodium dodecyl sulfate polyacrylamide gel electrophoresis, bovine diabetogenic peptide has a molecular weight of 24.000 daltons, slightly greater than that for prolactin. Amino acid analysis has revealed remarkable similarity between the diabetogenic peptide and prolactin; particularly in the numbers of residues of 1/2 cystine, proline, histidine and phenylalanine. The amino terminal amino acid sequence is methionyl-phenylalanyl-phenylalanine. By the criteria of molecular size, quantitative polyacrylamide gel electrophoresis, amino acid composition and amino terminal sequence analysis, we consider the relationship between the diabetogenic peptide and prolactin.