Monomeric G-protein

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A monomeric G-protein (also known as small G protein or small GTPases, is the umbrella term for a family of signal transducing proteins. These comprise of: Rab, Arf, Ras, Ran and Rho, which are also vital in the growth of cells, as well as cell transport, motility, cytokinesis and cell differentiation[1]. Monomeric G proteins comprise of three forms:

  1. an 'inactive' form in which the monomeric G-protein is bound to GDP (guanosine diphosphate), and
  2. In order to activate the inactive form of monomeric G-protein, a guanine exchange factor is needed.
  3. the 'active'  form in which the Monomeric G-protein is bound to GTP (guanosine triphosphate).

Notably, monomeric G-proteins are small (ranging around 20-25 kDa) compared with larger types of G protein like heterotrimeric proteins (which are typically 30-35 kDa)[2]. To inactivate a monomeric G protein, a GTPase activating protein (GAP) is required to hydrolyse the GTP to GDP as they have weak intrinsic GTPase activity.


  1. Berg et al., (2006) Biochemistry, 6th edition, New York. Pages 432
  2. Berg et al., (2006) Biochemistry, 6th edition, New York. Pages 433
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