cell division cycle 42 (Cdc42) is a small GTPase of the Rho family
Cdc42 is an essential GTPase that belongs to the Rho family of Ras-like GTPases. These proteins act as molecular switches by responding to exogenous and/or endogenous signals and relaying those signals to activate downstream components of a biological pathway. Cdc42 transduces signals to the actin cytoskeleton to initiate and maintain polarized growth and to mitogen-activated protein morphogenesis. In the budding yeast Saccharomyces cerevisiae, Cdc42 plays an important role in multiple actin-dependent morphogenetic events such as bud emergence, mating-projection formation, and pseudohyphal growth. In mammalian cells, Cdc42 regulates a variety of actin-dependent events and induces the JNK/SAPK protein kinase cascade, which leads to the activation of transcription factors within the nucleus. Cdc42 mediates these processes through interactions with a myriad of downstream effectors, whose number and regulation we are just starting to understand. In addition, Cdc42 has been implicated in a number of human diseases through interactions with its regulators and downstream effectors. Most Rho proteins contain a lipid modification site at the C-terminus, with a typical sequence motif CaaX, where a = an aliphatic amino acid and X = any amino acid. Lipid binding is essential for membrane attachment, a key feature of most Rho proteins. Due to the presence of truncated sequences in this CD, the lipid modification site is not available for annotation.