Reevaluation of the amino acid sequence of porcine follitropin.

We have reevaluated the sequence of porcine follicle-stimulating hormone (pFSH) with more recent protein-sequencing methodology. This has led to revision of the earlier proposed sequence. As with almost all reported gonadotropin alpha-subunits, NH2-terminal heterogeneity was found in the porcine FSH alpha-subunit (FSH alpha), starting with residue Phe (1), Asp (3), Gly (4), or Thr (7). In the beta-subunit, there were found to be at least two molecular species, starting with residue Asn (1) (minor 20%) or Cys (3) (major 80%) as NH2-terminal and ending at residue Glu (108) as COOH-terminal. The net effect of the present revisions is to increase the homology of pFSH beta with other reported follitropin sequences. Apparent differences in the half-cystine placements in a previous proposal for pFSH beta compared with other species of FSH are no longer tenable. The half-cystine placements thus remain a constant structural feature throughout the gonadotropin hormones (choriogonadotropin, follitropin, and lutropin).