ADRENAL CHROMAFFIN GRANULES - EVIDENCE FOR AN ULTRASTRUCTURAL EQUIVALENT OF THE PROTON-PUMPING ATPASE

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  • 1 January 1982
    • journal article
    • research article
    • Vol. 27  (1) , 96-104
Abstract
Adrenal chromaffin granules possess an F1-ATPase which according to biochemical criteria is very similar to the mitochondrial one. To find a morphological equivalent for this enzyme chromaffin granules from bovine adrenal medulla were subjected to negative staining and freeze-etching. With both methods globular particles of 8-9 nm diameter could be demonstrated on the surface of these organelles. A single granule possessed on average 22 particles. In negative staining the particles appeared separated from the membrane by a stalk of 8 nm. This typical morphological appearance was independent from a great variety of experimental procedures. After freeze-etching the particles were closely apposed to the membrane without any evidence for an interposed stalk. Pretreatment of chromaffin granules with pronase or trypsin led to a time dependent disappearance of the surface particles. In negative staining the stalked particles of chromaffin granules were very similar in structure and size to those of mitochondria which were already identified as F1-complexes. Based on this observation and other lines of evidence the stalked particles found on the surface of chromaffin granules apparently represent the F1-complex of the proton-pumping ATPase of these organelles.