Basudev Shome

Analysis of neutral sugars by gas-liquid chromatography of alditol acetates: Application to thyrotropic hormone and other glycoproteins

Abstract A method has been developed for the quantitative determination of the neutral sugars of several glycoproteins including thyrotropic hormone, thyroglobulin, and ovalbumin by gas-liquid chromatography of alditol acetates. This approach has the advantage that only one peak for each sugar is present in the chromatograms, which is particularly valuable in the determination of trace components. The same samples are analyzed for hexosamines by ion-exchange chromatography and the combination of methods permits analyses for all sugar components other than sialic acid on one or two milligrams of glycoprotein. In addition to the fucose and mannose previously reported, highly purified bovine thyrotropin contains approximately one-half residue of galactose per molecule with the human hormone purified by similar methods relatively richer in this sugar. Trace amounts of galactose have also been found in crystalline ovalbumin preparations further purified by chromatography.

Studies on the Structure of Thyrotropin: Its Relationship to Luteinizing Hormone

Publisher Summary This chapter describes the structure of thyrotropin and its relationship to luteinizing hormone (LH). The pituitary peptide hormones were among the first compounds to yield evidence for probable evolutionary relationships among proteins and peptides with different functions—that is, oxytocin and vasopressin; the corticotropins, melanotropins, and β-lipotropin; and more recently prolactin and growth hormone. The likelihood that follicle-stimulating hormone (FSH) contains subunits was recognized by Gray, and Papkoff and Ekblad reported that the FSH chain of LH may have common properties with a subunit of FSH. The dissociation of TSH and LH into two subunits raises a number of biological questions—for example, those concerning the control of biosynthesis of individual chains and the possible effects of releasing factors.

A reevaluation of the amino acid sequence of human follitropin β-subunit

A collaborative study from two laboratories has been undertaken to re-evaluate the human follitropin β-subunit sequence (hFSHβ), since areas of uncertainty remain in the wake of two earlier reports. The first report was by Shome and Parlow (1974). The second, by Saxena and Rathnam (1976), proposed revisions for sequence not definitively placed in the first study, as well as some differences in other placements. We have re-examined the sequence of the hFSHβ with more recent methodology. This has led to revision of certain areas of the sequence and resolution of differences between the two earlier proposals. Specifically, an-Ile-Ser- is established at 21–22, Asp at 41, Arg at 44, Lys at 46, and Glu at 111. These were areas of disagreement in the earlier proposals. A definitive placement of the residues around tryptophan-27 has now been obtained by three laboratories. C-terminal heterogeneity was observed with subunits ending at residue 107, 109, or 111. N-terminal heterogeneity has been observed in all preparations examined to date. A significant population of molecules with a proteolytic nick between residues 38–39 is noted. This is very likely an artifact of the collection and processing. The preparations examined in the present studies showed no evidence of residues 112–118 proposed by Saxena and Rathnam.

Bovine, human and porcine thyrotropins: Molecular weights, amino- and carboxyl-terminal studies☆

Abstract The molecular weights and end-group analyses of bovine, human, and porcine thyrotropins (TSH) are reported. Both the hormones and their S-carboxymethyl derivatives behave as physically homogeneous materials during sedimentation equilibrium runs in 6 m guanidine hydrochloride. The weight average molecular weights of all three thyrotropins are approximately 25,000. No evidence was found for separation into peptide chains of smaller molecular size after disulfide bond cleavage. In the absence of a dissociating agent bovine TSH exhibited concentration-dependent aggregation. End-group analyses were in agreement with the above and showed phenylalanine to be the major amino-terminal residue in both bovine and porcine thyrotropins. In human TSH, phenylalanine and valine were present in equal proportions. In addition, 0.1 to 0.2 moles of amino-terminal aspartic acid per mole of hormone was found in each case. The carboxyl-terminal sequences of bovine and human TSH are most probably -His-Tyr-Lys-Ser-Tyr-COOH; that of porcine TSH, -His-Tyr-Lys-Tyr-Ser-COOH. About 0.2 moles of methionine and leucine which could not be accommodated in the above sequences were also found at or near the carboxyl-termini of bovine and human TSH respectively. The amino acid and carbohydrate compositions of human and porcine TSH are compared with those of bovine TSH and purified human and bovine luteinizing hormones.