On the Heterogeneity of Beef Heart Cytochrome c. II. Some Physico-chemical Properties of the Main Subfractions (Cy I - Cy III).

Publisher Website
Google Scholar
Abstract
The heterogeneity of monomeric beef heart cytochrome c previously described, has been confirmed in the present study by moving-boundary electrophoresis in the pH range 8.0-11.2. The various subfractions are all strongly basic proteins, and their isoelectric points [pI(0[degree]C)] in borate buffer, [mu][image]0.1 were found to be Cy I: 10.78 (10.80), Cy II: 10.58 (10.60), Cy III: 10.36 (10.22) in the ferric (ferrous) form. The calculation of the true electrophoretic mobility of Cy I and Cy II is complicated by the fact that Cy I and Cy II are convertible to Cy II and Cy III, respectively, at pH [image] 9.3. From the curves of the mobility as a function of pH an estimate has been made of the number and nature of the ionizable groups which contribute to the difference in electrophoretic mobility of the subfractions. The difference in electrophoretic mobility of subfractions Cy II and Cy I is explained by the presence of one more negatively charged group (carboxyl) in Cy II than in Cy I since the latter contains one amide group more than the former. The difference in electrophoretic mobility of subfractions Cy III and Cy I is explained by the presence of 2 more negatively charged groups (carboxyl) in Cy III than in Cy I. The light absorption spectra of Cy II and Cy III reveal certain differences from those of Cy I characteristic of irreversible conformational changes. None of the subfractions Cy I-Cy III combine with carbon monoxide at neutral pH.