Isolation, Characterization and C-Terminal Sequence of Ovine Growth Hormone

Abstract

1 A procedure is described for the isolation of ovine growth hormone which involves: extraction of frozen pituitaries with borate buffer at pH 8.4, fractionation by ammonium sulphate precipitation and chromatography on DEAE cellulose. This is followed by removal of various impurities by isoelectric precipitation and by the addition of ethanol. The last step consists in a gel-filtration through a column of Sephadex G-100. 2 The protein obtained is homogeneous judged by free electrophoresis, ultracentrifugation, analytical dialysis and C-terminal amino acid analysis; only polyacrylamide gel electrophoresis reveals two minor components accompanying a major anionic band. It has an isoelectric pH of 6.3 and a weight average molecular weight of 20300. 3 The comparison of the amino acid compositions and of the tryptic peptide maps of ovine and bovine growth hormones indicates great homology between these two proteins. The C-terminal amino acid sequence in ovine growth hormone is as follows: (Phe,Glu,Gly)-Ala-Ser-Cys-Ala-Phe-OH.