4tv7
From Proteopedia
Crystal structure of Bacillus subtilis GabR at 2.05 Angstroms resolution
Structural highlights
Function[GABR_BACSU] Activates the transcription of the gabTD operon. Is also a repressor of its own expression, both in the presence and absence of GABA. Binds specifically to the DNA region overlapping the -35 region of the gabT promoter and the -10 and +1 regions of the gabR promoter. Principally regulates the utilization of gamma-aminobutyrate.[1] [2] Publication Abstract from PubMedMocR/GabR family proteins are widely distributed prokaryotic transcriptional regulators containing pyridoxal 5'-phosphate (PLP), a coenzyme form of vitamin B6. The Bacillus subtilis GabR, probably the most extensively studied MocR/GabR family protein, consists of an N-terminal DNA-binding domain and a PLP-binding C-terminal domain that has a structure homologous to aminotransferases. GabR suppresses transcription of gabR and activates transcription of gabT and gabD, which encode gamma-aminobutyrate (GAlphaBetaAlpha) aminotransferase and succinate semialdehyde dehydrogenase, respectively, in the presence of PLP and GABA. In this study, we examined the mechanism underlying GabR-mediated gabTD transcription with spectroscopic, crystallographic and thermodynamic studies, focusing on the function of the aminotransferase domain. Spectroscopic studies revealed that GABA forms an external aldimine with the PLP in the aminotransferase domain. Isothermal calorimetry demonstrated that two GabR molecules bind to the 51-bp DNA fragment that contains the GabR-binding region. GABA minimally affected DeltaG(binding) upon binding of GabR to the DNA fragment but greatly affected the contributions of DeltaH and DeltaS to DeltaG(binding). GABA forms an external aldimine with PLP and causes a conformational change in the aminotransferase domain, and this change likely rearranges GabR binding to the promoter and thus activates gabTD transcription. Role of the aminotransferase domain in Bacillus subtilis GabR, a pyridoxal 5'-phosphate-dependent transcriptional regulator.,Okuda K, Kato S, Ito T, Shiraki S, Kawase Y, Goto M, Kawashima S, Hemmi H, Fukada H, Yoshimura T Mol Microbiol. 2015 Jan;95(2):245-57. doi: 10.1111/mmi.12861. Epub 2014 Dec 8. PMID:25388514[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
| ||||||||||||||||||||
