ADENOSINE-TRIPHOSPHATASE ISOLATED FROM CHROMAFFIN-GRANULE MEMBRANES IS CLOSELY SIMILAR TO F1-ADENOSINE TRIPHOSPHATASE OF MITOCHONDRIA

An ATPase purified with high yield from bovine chromaffin granules closely resembles the mitochondrial F1‐ATPase from bovine heart or bovine adrenal medulla with respect to the following properties: apparent molecular weight on gel filtration, subunit composition on dodecyl‐ sulphate/polyacrylamide gel electrophoresis, cross‐reaction with an antiserum directed against F1‐ATPase from bovine heart mitochondria, and proteolytic fingerprints of the three largest subunits. The chromaffin granule ATPase could, however, be distinguished from the mitochondrial enzyme: it did not enhance the fluorescence of aurovertin and reacted differently from mitochondrial F1‐ATPase in quantitative complement fixation. The following three arguments make it unlikely that the ATPase isolated from chromaffin granules has been artifically dislodged from mitochondria during fractionation: (a) mitochondrial contamination of the purified chromaffin granule membranes was bhow 2%; (b) the purification procedure solubilized at least two thirds of the total ATPase activity of these membranes; (c) an antiserum directed against bovine mitochondrial F1‐ATPase inhibited the ATP‐driven uptake of 5‐hydroxytryptamine by resealed chromaffin granule ‘ghosts’. The proton‐translocating ATPase of chromaffin granules is thus almost identical to mitochondrial F1‐ATPase. This finding raises intriguing questions about the evolution of chromaffin granules and about the mechanisms by which the two enzymes are transported to different locations within the same cell. Copyright © 1979, Wiley Blackwell. All rights reserved