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.

References: 

  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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