GTPase Superfamily

Proteins of the GTPase superfamily are found in all plant, bacterial and animal systems. The following examples illustrate the central functions of the regulatory GTPases in the cell. 

The members of the GTPase superfamily show an extensively conserved reaction mechanism. A common trait is a switching function that enables a reaction chain to be switched on or off (review Bourne et al., 1990). 

The superfamily of GTPases with their more than hundred members are divided by sequence homologies, molecular weight and subimit structure into further (super)fa-milies. These are the families of the heterotrimeric G-proteins, the Ras/GTPase superfamily and the family of initiation and elongation factors (Fig. 5.13). 

Bourne, H.R., Sanders, D.A. and McCormick, F. The GTPase superfamily a conserved switch for diverse cell functions (1990) Nature 348, 125-132... 

Reprinted with permission from Nature (H. R. Bourne et al., The GTPase superfamily A conserved switch of diverse cell functions, Nature, 348 126, 1990). Copyright 1990 Macmillan Magazines Limited.)... 

H.R. Bourne, D.A. Sanders, and F. McCormick. 1991. The GTPase superfamily Conserved structure and molecular mechanism Yatwre 349 117-127. (PubMed)... 

Bourne HR, Sanders DA, McCormick F (1991) The GTPase superfamily conserved structure and molecular mechanism. In Nature 349 117—27... 

Switching Mediated by Guanine Nucleotide-Binding Proteins Another group of Intracellular switch proteins constitutes the GTPase superfamily. These proteins include monomeric Ras protein (see Figure 3-5) and the G subunit of the trimeric G proteins. Both Ras and G , are bound to the plasma membrane, function in cell signaling, and play a key role in cell proliferation and differentiation. Other members... 

Small GTP-binding proteins (ARF or Sari) belonging to the GTPase superfamily control polymerization of coat proteins, the initial step in vesicle budding (see Figure 17-9). After vesicles are released from the donor membrane, hydrolysis of GTP bound to ARF or Sari triggers disassembly of the vesicle coats. 

Dynamin, unlike many GTPase superfamily members, exhibits a relatively rapid basal rate of GTP hydrolysis that is not rate-limited by GTP binding or GDP dissociation. Also unique to dynamin GTPase family... 

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