RAB GTPase Activating Protein 1 (RABGAP1)

Rab6 GTPase regulates intracellular transport at the level of the Golgi apparatus, probably in a retrograde direction. Primary sequence analysis indicates that GAPCenA displays similarities, to both the yeast Rab GTPase activating proteins and to the spindle checkpoint proteins Saccharomyces cerevisiae Bub2p and Schizosaccharomyces pombe Cdc16p. GAPCenA is indeed a GAP, specifically active in vitro on Rab6 and, to a lesser extent, on Rab4 and Rab2 proteins. Immunofluorescence and cell fractionation experiments showed that GAPCenA is mainly cytosolic but that a minor pool is associated with the centrosome.GAPCenA was found to form complexes with cytosolic gamma-tubulin and to play a role in microtubule nucleation. GAPCenA may be involved in the coordination of microtubule and Golgi dynamics during the cell cycle.