A monoclonal antibody specific for the amino terminal sequence of human prorenin identifies a common epitope on renal and amniotic fluid inactive renins.
A synthetic nonapeptide corresponding to the predicted amino terminus of human prorenin was synthesized and used as an antigen in the production of mouse hybridomas. Forty-seven clones producing antibody to this peptide were identified and screened for ability to bind to partially purified amniotic fluid inactive renin in a soluble phase assay. None showed activity. One purified antibody, 4D3-3C4, was found to bind by Western blotting to renal and amniotic fluid inactive renins, molecular size 52 kDa, after gel electrophoresis in sodium dodecyl sulphate (SDS) following reduction with mercaptoethanol. In contrast, the anti-renin monoclonal antibody, R3-27-6, recognizes active renin, molecular size 38 kDa, and two inactive renin species, 42 kDa and 52 kDa, in the same renin preparations. Kidney and amniotic fluid apparently contain an inactive renin that possesses the complete prorenin sequence. These data indicate that high molecular weight inactive renin from both kidney and amniotic fluid contain an epitope, accessible to antibody only after denaturation, which represents the amino-terminal octapeptide sequence of prorenin. The inactive renin preparations tested also contain smaller fragments which either possess this epitope or do not, while still reacting with antibodies to active renin. It is likely that all these smaller inactive renin species are the result of proteolysis, either post-synthetic or in vitro.
Day, RP; Hui, KY; Gure, M; Carlson, WD; Dzau, VJ; Haber, E
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