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    Background:  

    Small GTPases are a super-family of cellular signaling regulators. Rac belongs to the Rho sub-family of GTPases that 

    regulate cell motility, cell division, and gene transcription. GTP binding increases the activity of Rac, and the hydrolysis 

    of GTP to GDP renders it inactive. GTP  hydrolysis is ai  ded by GTPase activating proteins (GAPs), while  exchange of

    GDP for GTP is facilitated by guanine nucleotide exchange  factors