title: The Agrobacterium tumefaciens transcription factor BlcR is regulated via oligomerization.
abstract: The Agrobacterium tumefaciens BlcR is a member of the emerging isocitrate lyase transcription regulators that negatively regulates metabolism of γ-butyrolactone, and its repressing function is relieved by succinate semialdehyde (SSA). Our crystal structure showed that BlcR folded into the DNA- and SSA-binding domains and dimerized via the DNA-binding domains. Mutational analysis identified residues, including Phe(147), that are important for SSA association; BlcR(F147A) existed as tetramer. Two BlcR dimers bound to target DNA and in a cooperative manner, and the distance between the two BlcR-binding sequences in DNA was critical for BlcR-DNA association. Tetrameric BlcR(F147A) retained DNA binding activity, and importantly, this activity was not affected by the distance separating the BlcR-binding sequences in DNA. SSA did not dissociate tetrameric BlcR(F147A) or BlcR(F147A)-DNA. As well as in the SSA-binding site, Phe(147) is located in a structurally flexible loop that may be involved in BlcR oligomerization. We propose that SSA regulates BlcR DNA-binding function via oligomerization.
authors.affiliation: Indiana University, Bloomington, Indiana 47405, USA.
authors.forename: Yi
authors.initials: Y
authors.lastname: Pan
authors.forename: Valena
authors.initials: V
authors.lastname: Fiscus
authors.forename: Wuyi
authors.initials: W
authors.lastname: Meng
authors.forename: Zhida
authors.initials: Z
authors.lastname: Zheng
authors.forename: Lian-Hui
authors.initials: LH
authors.lastname: Zhang
authors.forename: Clay
authors.initials: C
authors.lastname: Fuqua
authors.forename: Lingling
authors.initials: L
authors.lastname: Chen
mesh_terms: D015107:4-Butyrolactone / Q000235:genetics / Q000378:metabolism; D016960:Agrobacterium tumefaciens / Q000235:genetics / Q000378:metabolism*; D019943:Amino Acid Substitution; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism*; D020125:Mutation, Missense; D010449:Peptide Mapping / Q000379:methods; D055503:Protein Multimerization / Q000502:physiology*; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D020218:Response Elements / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D012097:Repressor Proteins; D015107:4-Butyrolactone