title: Proteomics analysis of growth hormone isoforms in the human pituitary.
abstract: In order to elucidate the roles of human growth hormone (hGH) in the normal (control) pituitary and in adenomas, the hGH isoforms in the human pituitary were analyzed with two-dimensional gel electrophoresis, immobilized metal affinity column (Ga(+3)) chromatography, mass spectrometry (MS), and bioinformatics. Twenty-four hGH-containing proteins, with significantly different expression proportions of their isoforms were found. The proportions of isoforms were as follows: isoform 1 (87.5%) > isoform 2 (8.1%) > isoform 3 (3.3%) > isoform 4 (1.1%). Deamidation of asparagine to aspartate was identified with matrix-assisted laser desorption/ionization-time of flight MS. Tandem mass spectrometry data demonstrated that hGH is a phosphoprotein (spot 6); phosphorylation was found at Ser-77 in the tryptic peptide (68)YSFLQNPQTSLCFSESIPTPSNR(90), at Ser-176 in the tryptic peptide (172)FDTNSHNDDALLK(184), and at Ser-132 in the peptide (126)SLVYGASDSNVYDLLK(141). The phosphorylation sites at Ser-77 and Ser-176 were consistent with computer-program predictions (NetPhos). These results provide novel clues for further studies of the functions, and mechanisms of action, of hGH in the human pituitary and in growth hormone-related diseases.
authors.affiliation: Charles B. Stout Neuroscience Mass Spectrometry Laboratory, University of Tennessee Health Science Center, Memphis, TN 38163, USA.
authors.forename: Xianquan
authors.initials: X
authors.lastname: Zhan
authors.forename: Francesco
authors.initials: F
authors.lastname: Giorgianni
authors.forename: Dominic M
authors.initials: DM
authors.lastname: Desiderio
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D019295:Computational Biology; D019382:Human Growth Hormone / Q000032:analysis* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D010902:Pituitary Gland / Q000737:chemistry*; D020033:Protein Isoforms / Q000032:analysis* / Q000235:genetics / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D020543:Proteome / Q000032:analysis*; D040901:Proteomics; D020539:Sequence Analysis, Protein
chemical_list: D020033:Protein Isoforms; D020543:Proteome; D019382:Human Growth Hormone