Structural Studies on Bovine Growth Hormone

Purified bovine growth hormone, consisting of a single polypeptide chain, has been found to contain NHz-terminal alanine, phenylalanine, and methionine in nearly equal amounts. The minimum molecular weight calculated from its amino acid composition is 20,846. Five unique fragments have been prepared from bovine growth hormone by cleavage at 4 methionyl residues with cyanogen bromide. In the order of their elution from Sephadex G-50 and G-75, these have been designated Fragment A, with 109 amino acids ; Fragment B, 31 amino acids ; Fragment C, 25 amino acids; Fragment D, 12 amino acids; and Fragment E, a pentapeptide. Partial characterization of these fragments indicates a high degree of similarity between this molecule and human growth hormone. Isolation of tryptic peptides derived from Fragment C lends additional support to the apparent homology.