The GTPase superfamily: a conserved switch for diverse cell functions

Article Abstract:

A family, or group, of proteins has been identified and given the name the GTPases. These proteins bind and utilize GTP (guanosine triphosphate), and are regulated by the binding of GTP. The structure of the GTPases, and the regulation of the turning on or off of the protein by binding of GTP, has been conserved throughout evolution. It is conserved in simple organisms such as bacteria and yeast, as well as in more complex animals such as flies and vertebrates, including man. The GTPases are coupled to and regulate other proteins that are involved in many cellular functions including: the synthesis of proteins; the transmission of signals by hormones or light into the cell; the passage of proteins through organelles in the cell so they can eventually be utilized by the body; the control of cell maturation or differentiation and cell growth; and the transport of vesicles that are necessary for secretion of proteins outside of the cells. Some of these GTPases, such as the ras and NF1 gene, if mutated, (genetically changed), are oncogenes, genes that are involved in the abnormal growth of cells in cancer. It is thought that further research will identify additional GTPases and their involvement in additional cellular functions. (Consumer Summary produced by Reliance Medical Information, Inc.)

Phosphatases, Oncogenes, GTP

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How receptors turn Ras on

Article Abstract:

From tyrosene kinase to Ras, signals are transmitted through specific protein-protein interaction. Grb2 plays a role in enlisting Ras activator to form a stable complex. Analysis of signalling in mammalian cells predicted the flow of information from tyrosine kinases to Ras proteins. The components of the pathways are used to detect multiple signals, Ras is where the signals must pass. A puzzling aspect is that a variety of tyrosine kinases could funnel signals into the same Ras, which was unravelled by identification of 'Src homology' and 'adaptor protein'.

Column, Protein binding, Protein tyrosine kinase, Protein-tyrosine kinase

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An essential role for Rac in Ras transformation

Article Abstract:

The transformation activity of the oncogenic Ras depends on the activity of the GTPase Rac1. The Rat1 fibroblast Asn-17 Rac1 (Rac1 present with the Asn on the 17th position) cell line show suppression of the focus-formation by oncogenic Ras. However, the focus formation activity of the Raf kinase RafCAAX, is not affected. Assays done on focus-formation show that the activity of Val-12 Rac1 is related to that of RafCAAX. Thus, the transformation of the actin cytoskeleton is by the action of the Rac and MAP-kinase pathways controlled by Ras.

Proteins

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