Association of a 24-kDa GTP-binding protein, Gn24, with human platelet alpha-granule membranes.
Human platelets were disrupted using nitrogen cavitation and fractionated on sucrose density gradients to permit isolation of alpha-granules, the major secretory granule of platelets. Membrane proteins prepared from intact alpha-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 [alpha-32P]GTP. Two low molecular mass GTP-binding proteins with molecular mass of 27 and 24 kDa, respectively, were identified on the alpha-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 alpha-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.
Department of Pediatrics, McMaster University, Hamilton, Ontario, Canada.
J
J
van der Meulen
R P
RP
Bhullar
K A
KA
Chancellor-Maddison
D001792:Blood Platelets / Q000378:metabolism* / Q000648:ultrastructure; D002499:Centrifugation, Density Gradient; D003594:Cytoplasmic Granules / Q000378:metabolism* / Q000648:ultrastructure; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006801:Humans; D015151:Immunoblotting; D007425:Intracellular Membranes / Q000378:metabolism*; D008854:Microscopy, Electron
D019204:GTP-Binding Proteins