Biological activities of CNBr fragments of a major protein secreted from the rat seminal vesicle epithelium

Two fragments of SV-IV, one of the major proteins secreted from the rat seminal vesicle epithelium, were produced in vitro by protein cleavage with CNBr at level of the single methionine residue (Met-70) occurring in its polypeptide chain. After their purification by reversed-phase chromatography, SV-IV/A (1-70 fragment) and SV-IV/B (71-90 fragment) were assayed as transglutaminase substrates, and their anti-inflammatory, anti-thrombotic and immunosuppressive properties were evaluated in comparison with native SV-IV. Both fragments retained the SV-IV ability to act as transglutaminase substrates in vitro; fast atom bombardment mass spectrometry analyses of the reaction products pointed to Gln-9 and Gln-86 as acyl donor sites, and to Lys-59, -79 and -80 as acyl acceptor sites. In contrast, only SV-IV/A was shown to possess, like SV-IV, the property of inhibiting both the intensity of the carrageenin-induced rat foot edema and the platelet aggregation induced in vivo by different agents. Finally, the two protein fragments were found to be completely unable to inhibit both the mitogen-induced proliferation of human T cells and the mixed lymphocyte reaction.