STUDIES ON PITUITARY FOLLITROPIN .5. ISOLATION OF THE SUBUNITS OF THE HUMAN HORMONE AND REACTION OF THE AMINO-GROUPS WITH ACYLATING AGENTS

  • 1 January 1979
    • journal article
    • research article
    • Vol. 13  (4) , 394-402
Abstract
The .alpha. and .beta. subunits of human follitropin were isolated in a high state of purity. The tryptophan fluorescence of the native hormone and the isolated .beta. subunit are different. The N-terminus of the .alpha. and .beta. subunits was identified as valine and aspartic acid, respectively. While recombination of the isolated .alpha. and .beta. subunits restores the electrophoretic mobility of the intact hormone, its receptor binding activity cannot be fully regenerated. Substitution of the human follitropin .alpha. by an ovine lutropin .alpha. subunit, to form a recombinant with the follitropin .beta. subunit, generates a complex with 2-3 receptor binding activity of the native human follitropin and the same activity as ovine follitropin. Acylation of the intact hormone does not disrupt the quaternary structure but leads to complete inactivation. Acylation studies with the subunits suggests the crucial role of the .epsilon.-amino groups of the .alpha. subunit in determining biological activity.

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