Sequences of pituitary and placental lactogenic and growth hormones: evolution from a primordial peptide by gene reduplication

Human placental lactogen has been found to resemble human pituitary growth hormone very closely in amino acid sequence, about 80% of the residues examined being identical in the two molecules when a revised sequence for growth hormone is used as the basis for comparison. The structural features responsible for the differing biological potency of the two hormones may therefore reside in rather limited regions of primary structure. The observation of internal sequence homologies within the pituitary growth hormone and prolactin and the placental lactogen molecules suggests that these polypeptide hormones may have evolved by genetic reduplication from a smaller common ancestral peptide. This finding directs further attention to subfragments of these molecules as possible possessors of intrinsic somatotrophic and lactogenic activity.

Synthesis of a biologically active N-terminal tetratriacontapeptide of parathyroid hormone

Determination of the amino acid sequence of bovine parathyroid hormone has led to the synthesis of a tetratriacontapeptide corresponding to the amino-terminal 1-34 residues of the native molecule. The specific biological effects of this synthetic peptide on bone and kidney are qualitatively identical to those of the native hormone in classical bioassays in vivo and in several systems in vitro. Potency of the synthetic peptide equals or exceeds that of a biologically active fragment of comparable size isolated from the native hormone; the synthetic and natural peptides show complete immunological cross-reactivity. Thus, essential requirements for the physiological actions of the peptide on both skeletal and renal tissue are contained within the 34 amino-terminal amino acids. The potency of the synthetic peptide, relative to that of the native (84-amino acid) polypeptide, is greater in vitro than in vivo; this suggests that the carboxyl terminal two-thirds of the native hormone may protect the circulating polypeptide from rapid metabolic degradation.

The N-terminal amino acid sequence of two avian leukosis group specific antigens

Two group-specific antigenic proteins from an avian leukosis virus have been compared by amino acid analysis, tryptic peptide fingerprinting, and N-terminal sequence determination, and found to be dissimilar. There was microheterogeneity in the structure of the protein gs-b at residues 6; threonine and glutamic acid were found.

Isolation of a second avian leukosis group-specific antigen (gs-b) from avian myeloblastosis virus

Gs-b, a second group-specific antigenic protein of the avian leukosis group, has been isolated from Tween 80-ether treated avian myeloblastosis virus by Sephadex and carboxymethylcellulose chromatography, and compared by immunological and chemical means with the antigen (gs-a) described previously.