Human pituitary growth hormone. XXVII. Reaction with tetranitromethane

Involvement of lysine residues in the binding of hGH and bGH to somatotropic receptors

The biological activities of human (hGH) and bovine (bGH) growth hormone derivatives obtained by chemical modification of the lysine residues were studied by radioreceptor assays using rabbit liver homogenates for somatotropic activity (SA). Control treatment with BH4 had a very slight effect on the SA, whereas the methylation and ethylation drastically reduced the activity of both hormones. Guanidination of these hormones and even acetimidination at a lower rate are accompanied by a considerable loss of biological activity. These results show the involvement of lysine residues in the interaction of hGH and bGH with somatotropic receptors. The structure-function relationship of these molecules is discussed, suggesting that the lysine or arginine residues in positions 41, 64, 70 and 115 might be particularly implicated.

A proton-nuclear-magnetic-resonance study of human somatotropin (growth hormone). Assignment and properties of the histidine residues

The 1H-n.m.r. spectra of human somatotropin (growth hormone) show perturbed peaks from individual aromatic and aliphatic apolar residues, characteristic of a specifically folded globular structure. The imidazole C-2-H resonances of the histidine residues (at positions 18, 21 and 151 in the somatotropin sequence) were individually resolved, and their titration behaviour in the pH range 1.2-11.5 was investigated. The imidazole C-2-H resonance of histidine-151 is assigned, by comparison of its titration behaviour in human somatotropin and desamido-somatotropin (Asn-152 leads to Asp-152). The C-2-H resonances of all three histidine residues are assigned, by comparison of their relative deuterium-exchange rates (determined by n.m.r.) and the relative tritium-exchange rates of the histidine residues (determined by tryptic digestion of tritiated human somatotropin and reversed-phase high-pressure liquid-chromatographic separation of the histidine-containing tryptic peptides). There is evidence that histidine-18 forms an ion-pair bond with a glutamic acid or aspartic acid residue. The globular structure does not appear to change from pH3 to 11.5, though there is evidence for an unfolding of a region of the structure (involving histidine-21 and a tyrosine residue) below pH3.

Human growth hormone: 1974-1981

Chemical investigations of the human growth hormone (HGH) molecule were briefly reviewed for th period between 1974 and 1981. These include chemical modification, selective enzymic cleavage, the 20K HGH, synthetic peptide fragments, complementation of the natural NH2-terminal 134-amino acid fragment with natural or synthetic COOH-terminal fragments of various chain lengths, covalent reconstitution of two contiguous fragments of HGH with thrombin and bacterially synthesized methionyl-HGH.