Structural highlights
Function
[RELA_STREQ] In eubacteria ppGpp (guanosine 3'-diphosphate 5-' diphosphate) is a mediator of the stringent response that coordinates a variety of cellular activities in response to changes in nutritional abundance. This enzyme catalyzes both the formation of pppGpp which is then hydrolyzed to form ppGpp, and the hydrolysis of ppGpp. The enzyme does not similtaneously display both synthase and hydrolase activities. In the structure of residues 1-385 there are 2 conformations seen, the hydrolase-OFF/synthase-ON and hydrolase-ON/synthase-OFF, suggesting there is ligand-induced signal transmission between the 2 active sites.
Evolutionary Conservation
Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf.
Publication Abstract from PubMed
Enzymes of the Rel/Spo family enable bacteria to survive prolonged periods of nutrient limitation by producing an intracellular signaling alarmone, (p)ppGpp, which triggers the so-called stringent response. Both the synthesis of (p)ppGpp from ATP and GDP(GTP), and its hydrolysis to GDP(GTP) and pyrophosphate, are catalyzed by Rel/Spo proteins. The 2.1 A crystal structure of the bifunctional catalytic fragment of the Rel/Spo homolog from Streptococcus dysgalactiae subsp. equisimilis, Rel(Seq), reveals two conformations of the enzyme corresponding to known reciprocal activity states: (p)ppGpp-hydrolase-OFF/(p)ppGpp-synthetase-ON and hydrolase-ON/synthetase-OFF. The hydrolase and synthetase domains bear remarkable similarities to the catalytic domains of the cyclic phosphodiesterase and nucleotidyltransferase superfamilies, respectively. The active sites, separated by more than 30 A, contain bound nucleotides including an unusual (p)ppGpp derivative, GDP-2':3'-cyclic monophosphate. Reciprocal regulation of the antagonistic catalytic activities, suggested by the structure, is supported by mutagenesis experiments and appears to involve ligand-induced signal transmission between the two active sites.
Conformational antagonism between opposing active sites in a bifunctional RelA/SpoT homolog modulates (p)ppGpp metabolism during the stringent response [corrected].,Hogg T, Mechold U, Malke H, Cashel M, Hilgenfeld R Cell. 2004 Apr 2;117(1):57-68. PMID:15066282[1]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Hogg T, Mechold U, Malke H, Cashel M, Hilgenfeld R. Conformational antagonism between opposing active sites in a bifunctional RelA/SpoT homolog modulates (p)ppGpp metabolism during the stringent response [corrected]. Cell. 2004 Apr 2;117(1):57-68. PMID:15066282
