Association of a 24‐kDa GTP‐binding protein, Gn24, with human platelet α‐granule membranes

Publisher Website
Google Scholar
Abstract
Human platelets were disrupted using nitrogen cavitation and fractionated on sucrose density gradients to permit isolation of α‐granules, the major secretory granule of platelets. Membrane proteins prepared from intact α‐granules by alkali extraction were separated by SDS‐polyacrylamide gel electrophoresis, transferred to nitrocellulose and the blot probed for the presence of GTP‐binding proteins using [α‐32P]GTP. Two low molecular mass GTP‐binding proteins with molecular mass of 27 and 24 kDa, respectively, were identified on the α‐granule membrane. In contrast to the 27‐kDa protein which was present in significant amounts in the plasma membrane‐enriched fraction, the 24‐kDa protein showed a preferential association with the α‐granule membrane. On immunoblotting with specific antiserum, the 24‐kDa GTP‐binding protein was found to be distinct from rab3A. To the best of our knowledge, the present report represents the first identification of low molecular mass GTP‐binding proteins associated with a platelet secretory granule.