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Publication Abstract from PubMed

GTPases (G proteins) hydrolyze the conversion of GTP to GDP and free phosphate, a process integral in prokaryotic and eukaryotic signaling, protein biosynthesis, cell division, and membrane transport processes. The G protein cycle is brought to a halt after GTP hydrolysis, and requires the release of GDP before a new cycle can be initiated. For eukaryotic heterotrimeric Galphabetagamma proteins, the interaction with a membrane bound G protein coupled receptor (GPCR) catalyzes the release of GDP from the Galpha subunit. Structural and functional studies have implicated one of the nucleotide binding sequence motifs, the G5 motif, to play an integral part in this release mechanism. Indeed, a Galphas G5 mutant (A366S) was shown to have an accelerated GDP release rate, mimicking a GPCR catalyzed release state. Here we investigate the role of the equivalent residue in the G5 motif (residue A143) in the prokaryotic membrane protein FeoB from Streptococcus thermophilus, which includes an N-terminal soluble G protein domain. The structure of this domain has previously been determined in the apo and GDP-bound states and in the presence of a transition state analogue, revealing conformational changes in the G5 motif. The A143 residue was mutated to a serine and analyzed with respect to changes in the GTPase activity, nucleotide release rate, GDP affinity, and structural alterations. We conclude that the identity of the residue at this position in the G5 loop plays a key role in the nucleotide release rate by allowing the correct positioning and hydrogen bonding of the nucleotide base. This article is protected by copyright. All rights reserved.

Structural And Functional Analysis Of A Feob A143s G5 Loop Mutant Explains Accelerated Gdp Release Rate.,Guilfoyle AP, Deshpande CN, Vincent K, Pedroso MM, Schenk G, Maher MJ, Jormakka M FEBS J. 2014 Mar 20. doi: 10.1111/febs.12779. PMID:24649829^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.