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A 56,000-dalton renin-binding protein in hog kidney is an endogenous renin inhibitor.

1981; Elsevier BV; Volume: 256; Issue: 23 Linguagem: Inglês

10.1016/s0021-9258(18)43227-9

1083-351X

Naoto Ueno, Hitoshi Miyazaki, Shinichi Hirose, K Murakami,

Hormonal Regulation and Hypertension

Renin-binding protein (RBP) inhog kidney was characterized and identified as a renin inhibitor.The molecular weight (Mr) of RBP is 56,000 when estimated by gel filtration.Its isoelectric point is 4.9.Upon binding to renin, it forms a renin*RBP complex with M, = 113,000 as revealed by sedimentation equilibrium using an air-driven ultracentrifuge (Airfuge).The renin RBP complex, formed by incubating hog kidney extract at 37 "C, is inactive when assayed with little dilution.On extensive dilution, however, this complex dissociates and acquires renin activity.The equilibrium between renin and renin-RBP complex and the equilibration rate were also studied by high performance liquid chromatographic gel filtration.The equilibrium was shifted to the complex, suggesting that RBP is present in an excess of renin in the kidney.The complex was shown to dissociate during the gel filtration due to rapid equilibration.Therefore, the elution position of the complex varied depending on flow rates, thereby making it difficult to determine the M, of the complex by gel filtration.The renin-RBP complex is unlikely to occur in the normal kidney because renin and RBP are localized in the granule and cytosol fractions, respectively.RBP may provide security against accidental rupture of renin granules under abnormal circumstances.Renin, an aspartic protease, plays an important role in blood pressure regulation.The enzyme cleaves its substrate, angiotensinogen, to produce the decapeptide angiotensin I which is then converted to the potent vasoconstrictor angiotensin 11 by the action of converting enzyme.Renin-binding protein has been demonstrated in various mammalian kidneys (1-3) and shown to have a binding capacity specific for renin