Endocrinology, Vol 127, 2985-2989, Copyright © 1990 by Endocrine Society

ARTICLES

The antigenic structure of the human glycoprotein hormone alpha- subunit: II. Cross-species comparisons

ER Bergert, B Madden, DJ McCormick, H Papkoff and RJ Ryan
Department of Biochemistry and Molecular Biology, Mayo Medical School, Rochester, Minnesota 55905.

Eight monoclonal antibodies, specific for the glycoprotein hormone alpha-subunit, were raised against human free alpha-subunit, human FSH, or human CG. All of these antihuman monoclonal antibodies were tested for cross-reactivity with alpha-subunits derived from bovine, porcine, equine, bull frog, sea turtle, turkey, and ostrich glycoprotein hormones. All showed cross-reactivity with affinities ranging from 10(- 4) to 10(-8) depending upon the antibody and the species of alpha- subunit. Cyanogen bromide fragments of bovine and equine alpha, when tested with selected antibodies indicated that antigenic determinants could be localized in two regions: alpha 9-33 and alpha 76-92. Comparison of amino acid sequences, and relative potencies, suggest that major antigenic determinants involve residues 21, 22, and 23 (F-F- S in human alpha) and 76-85 (G-G-F-K-V-E-N-H-T-A in human alpha). As part of this study the N-terminal amino acid sequences of bull frog, sea turtle, turkey, and ostrich alpha-subunits were determined and reported for the first time.