2 FORMS OF CYTOPLASMIC ACTIN IN ADRENAL CHROMAFFIN CELLS

Chromaffin cells were isolated from bovine adrenal medullae and actin present in the cytosol of these cells was purified by affinity chromatography on deoxyribonuclease I-Sepharose 4B. Isoelectric focusing and two-dimensional gel electrophoresis showed that chromaffin cell actin is composed of two (β and γ) isomeric forms which have the same molecular weight as muscle (α)-actin but different isoelectric points. Muscle type α-actin, which is the most acidic form of actin, was not present in chromaffin cells. The difference between the isoelectric points of the actins is smaller than 0.1 pH unit. Moreover, there is approximately 10% more β-actin than γ-actin present in the chromaffin cell cytosol. The possible role of these two isomeric actins in the chromaffin cell is discussed. © 1979.