Amino acid sequence of the beta subunit of follicle-stimulating hormone from human pituitary glands.

The beta subunit of follicle-stimulating hormone (FSH-beta) from human pituitary glands was reduced and S-aminoethylated prior to thermolytic, tryptic, and chymotryptic digestions. Each digest was gel-filtered on Sephadex G-50 to seperate the glycopeptides. The glycopeptides and the peptides were isolated by high voltage paper electrophoresis at pH 6, 3.5, and 2.0. The purity of the isolated peptides was confirmed by amino acid analyses. The amino acid sequences of peptides were determined by Edman degradation followed by subtractive amino acid analysis and, in certain cases, confirmed by dansylation. COOH-terminal sequences of the peptides were determined by digestion with carboxypeptidases A and B and by hydrazinolysis. The tryptophan content of human follicle-stimulating hormone, of the beta subunit of human follicle-stimulating hormone, and of the glycopeptides obtained from the enzymic digests was determined by fluorescence spectra, titration against N-bromosuccinimide, colorimetric estimation with p-dimethyl aminobenzaldehyde, hydrolysis with methane sulfonic acid containing 0.2% tryptamine followed by amino acid analysis, microbiological assay, and sequence analysis. The presence of 1 tryptophan residue in the beta subunit was indicated.