6gz2
From Proteopedia
Crystal Structure of the LeuO Effector Binding Domain
Structural highlights
Function[LEUO_ECOLI] A global transcription factor. Activates transcription of the 9 following operons; yjjQ-bglJ, yjjP, acrEF, ybdO, yjcRQP, casABCDE12, rhsD-ybbC, fepE and gltF, in most cases it probably interferes with silencing by H-NS and activates transcription. Represses transcription of the 3 following operons; uxaCA, sdaCB and btsT. H-NS repression of the bgl operon, leading to the ability to metabolize some beta-glucosides. It also directly activates the bgl operon. Activation is H-NS and BglJ-RcsB independent.[1] [2] [3] [4] Publication Abstract from PubMedLeuO is a pleiotropic LysR-type transcriptional regulator (LTTR) and co-regulator of the abundant nucleoid-associated repressor protein H-NS in Gammaproteobacteria. As other LTTRs, LeuO is a tetramer that is formed by dimerization of the N-terminal DNA-binding domain (DBD) and C-terminal effector-binding domain (EBD). To characterize the Escherichia coli LeuO protein, we screened for LeuO mutants that activate the cas (CRISPR-associated/Cascade) promoter more effectively than wild-type LeuO. This yielded nine mutants carrying amino acid substitutions in the dimerization interface of the regulatory EBD, as shown by solving the EBD's crystal structure. Superimposing of the crystal structures of LeuO-EBD and LeuO-S120D-EBD suggests that the Ser120 to Asp substitution triggers a structural change that is related to effector-induced structural changes of LTTRs. Corresponding functional analyses demonstrated that LeuO-S120D has a higher DNA-binding affinity than wild-type LeuO. Further, a palindromic DNA-binding core-site and a consensus sequence were identified by DNase I footprinting with LeuO-S120D as well as with the dimeric DBD. The data suggest that LeuO-S120D mimics an effector-induced form of LeuO regulating a distinct set of target loci. In general, constitutive mutants and determining the DNA-binding specificity of the DBD-dimer are feasible approaches to characterize LTTRs of unknown function. Characterization of the pleiotropic LysR-type transcription regulator LeuO of Escherichia coli.,Fragel SM, Montada A, Heermann R, Baumann U, Schacherl M, Schnetz K Nucleic Acids Res. 2019 Jun 11. pii: 5513778. doi: 10.1093/nar/gkz506. PMID:31184713[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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