RAS p21 proteinski aktivator 1 ili RasGAP (aktivirajući protein Ras GTPaze), takođe poznat kao RASA1, je 120-kDa citosolni ljudski protein koji ima dve glavne aktivnosti:
Inakctivacija Ras proteina iz njegove aktivne GTP-vezane forme do njegove neaktivne GDP-vezane forme pojačavanjem endogene GTPazne Ras aktivnosti, preko njegovog C-terminalnog GAP domena
Mitogena transmisija signala u smeru daljih interakcionih partnera putemn njegovih N-terminalnih SH2-SH3-SH2 domena
Protein kodiran ovim genom je lociran u citoplazmi i deo je GAP1 familije GTPazno-aktiviranih proteina. Ovaj genski produkt stimuliše GTPaznu aktivnost normalnog RAS p21, ali ne i njegovog onkogenog pandana. Delujući kao supresor RAS funkcije, ovaj protein pojačava slabu unutrašnju GTPaznu aktivnost RAS proteina, što dovodi do inaktiviranje GDP-vezane forme RAS-a, čime pospešuje kontrolu ćelijske proliferacije i diferencijacije. Mutacije koje dovode do promena u mestima vezivanja ovog proteina su vezane za bazalne ćelijske kacinome. Alternativnim splajsovanjem se formiraju dve izoforme, pri čemu kraća izoforma, kojoj nedostaje N-terminusni hidrofobni region zadržava aktivnost. Ona je izobilno izražena u materičnim, ali ne i odraslim tkivima.[1]
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