Conformations of bradykinin in relation to solvent environmnet

Abstract

Isolation of glomeruli was done by microdissection. Tubuli were isolated after "dissociative" treatment with collagenase, according to Guder. (Hoppe-Seyler's 2. PhysioI. Chemie 352,1319Chemie 352, 1971. We observed a linear dose dependency of enzyme in microdissected glomeruli and in isolated tubuli. Enzyme activity of 80 glomeruli was the lowest measurable. 90% in inhibition of Kinin formation was observed by the use of Trasylol. Carboxypeptidase B completey destroyed the uterus contracting material. There was no effect on rat blood pressure even after application of an incubation mixture with high doses of urine glomeruli and tubuli. Renin and Angiotensin II was not detectable. There were several hints of a tubular Iocalisation of renal Kininogenase. Now it is evident, that renal Kininogenase is located in glomeruli as well as in tubuli. Bradykinin has different spectroscopic properties in polar compared to non-polar environments. These spectroscopic differences are assumed to reflect a reorientation of the amide dipoles with respect to each other and with respect to the solvent environment. This assumption is based on analogy with spectroscopic changes known to occur in model polypeptides such as poly-~'-benzyI-L-glutamate in solvents of differingoolarity. Strong evidence has been accumulated from biophysical studies which indicates that the conformations of cyclic depsipeptides differ in polar and non-polar environments and also when complexed with a cation. These transitions have been related to the ion-transport properties of the depsipeptides indicating conformational changes of the depsipeptides upon association with the hydrophobic environment in a membrane. Similarly, the apparent conformation changes of bradykinin associated with the change from polar to non-polar solvents may reflect possible changes involved in its pharmacological effects. In addition we have found that sodium dodecyl sulfate (SDS)induces changes in the circular dichroism (CD) spectrum of bradykinin equivalent to those found in non-polar solvents. SDS in association with proteins has been suggested by Reynolds and Tanford (J. Biol. Chem., 1970, 245, 5161) to provide a model system for studies of the conformational properties of membrane-associated proteins. Analogs of bradykinin where small modification have been carried out on the proline residue in the third position from the cx-amino terminal demonstrate different aqueous CD spectra from the parent