GTP‐binding Loop

Guangpu Li, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA

Published online: March 2003

DOI: 10.1038/npg.els.0003052

The GTP-binding loop is an evolutionarily conserved structure found in the GTPase superfamily of proteins. The GTP-binding loop enables GTPases to bind and hydrolyse GTP molecules and makes them excellent regulators of cellular processes.

Keywords: GTPase; GTP hydrolysis; guanine nucleotide; molecular switch; Ras

Figure 1. Primary and secondary structures of human H-Ras protein. The amino acid sequence of the Ras protein is shown in single-letter code. The locations of helices and strands are indicated above the corresponding amino acid sequences. The locations of G loops are indicated below the corresponding amino acid sequences.
Figure 2. Ras structures in three dimensions. (a) Crystal structure of Ras complexed with the GTP analogue guanosine-5¢-(,-imido) triphosphate (GppNp) (Pai et al., 1990). The main chain is represented by ribbons with the five G loops in red, the six strands in yellow, and the remaining portion in white. The side-chains of selected amino acid residues in the G loops are depicted with orange space-filled models. The bound GppNp is indicated (as ball and stick form) in blue, while the  Mg2+ near the -phosphate is indicated in green. (b) Crystal structure of Ras complexed with GDP (Milburn et al., 1990). The major differences of this structure from the Ras-GppNp complex are the bound nucleotide GDP (in light green) and the conformational changes in the switch regions as indicated. The other regions are depicted as for the Ras-GppNp structure in (a). (Figure courtesy of Timothy Mather.)
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 Further Reading
    Bourne HR, Sanders DA and McCormick F (1991) The GTPase superfamily: conserved structure and molecular mechanism. Nature 349: 117–126.
    Sprang SR (1997) G protein mechanisms: insights from structural analysis. Annual Review of Biochemistry 66: 639.
    book Wittinghofer A (2000) "The functioning of molecular switches in three dimensions". In: Hall A (ed.) GTPases, pp. 244–310. New York: Oxford University Press

Related Sub-Topics:

Protein Structure | Biomolecular Interactions | Proteins: Structure, Function, Metabolism
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Article Title: GTP‐binding Loop
 
How to Cite close
Li, Guangpu(Mar 2003) GTP‐binding Loop. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1038/npg.els.0003052]