Two fragments from fibrinolysin digests of ovine prolactin: characterization and recombination to generate full immunoreactivity.

The action of fibrinolysin (plasmin; EC 3.4.21.7) on ovine prolactin has been investigated. It was found that the enzyme selectively cleaves the bond between Met-53 and Ala-54. The two fragments, PRL-(1-53) and PRL-(54-199), have been purified and characterized. A recombinant molecule has been obtained by noncovalent interaction of PRL-(1-53) and PRL-(54-199). The recombined protein behaves nearly identically to the parent hormone in circular dichroism spectra and exclusion chromatography. The recombinant possesses full immunoreactivity, as revealed by gel double-diffusion and complement fixation. However, the recombined protein exhibits low prolactin activity in the pigeon crop-sac test.