Dissociation of Some of the Biological Activities of Porcine and Human Growth Hormones by Cyanogen Bromide Cleavage12

Highly purified porcine (PGH) and human (HGH) growth hormones were reduced,S-aminoethylated and cleaved with cyanogen bromide. The two largest fragments resulting from the cleavage of PGH were separated from the reaction mixture and purified. These were porcine fragment A (about 112 residues) beginning at the fifth residue from the N-terminus and fragment B (55 residues), which follows fragment A in the sequence of the PGH molecule. The largest fragment resulting from the cleavage of HGH, human fragment A (111 residues), was also prepared in purified form. Human fragment A and porcine fragment A represent roughly equivalent portions of their respective hormone molecules. These purified fragments were then tested for biological activity. Porcine fragment A, when injected intraperitoneally into hypophysectomized rats, stimulated the in vivo incorporation of 14C-leucine into the protein of the diaphragm and liver. Also, both porcine fragment A and human fragment A stimulated the in vitro incorporation of leu...