Structural and biochemical study of effector molecule recognition by the E.coli glyoxylate and allantoin utilization regulatory protein AllR.
The interaction of Escherichia coli AllR regulator with operator DNA is disrupted by the effector molecule glyoxylate. This is a general, yet uncharacterized regulatory mechanism for the large IclR family of transcriptional regulators to which AllR belongs. The crystal structures of the C-terminal effector-binding domain of AllR regulator and its complex with glyoxylate were determined at 1.7 and 1.8 A, respectively. Residues involved in glyoxylate binding were explored in vitro and in vivo. Altering the residues Cys217, Ser234 and Ser236 resulted in glyoxylate-independent repression by AllR. Sequence analysis revealed low conservation of amino acid residues participating in effector binding among IclR regulators, which reflects potential chemical diversity of effector molecules, recognized by members of this family. Comparing the AllR structure to that of Thermotoga maritima TM0065, the other representative of the IclR family that has been structurally characterized, indicates that both proteins assume similar quaternary structures as a dimer of dimers. Mutations in the tetramerization region, which in AllR involve the Cys135-Cys142 region, resulted in dissociation of AllR tetramer to dimers in vitro and were functionally inactive in vivo. Glyoxylate does not appear to function through the inhibition of tetramerization. Using sedimentation velocity, glyoxylate was shown to conformationally change the AllR tetramer as well as monomer and dimer resulting in altered outline of AllR molecules.
Ontario Center for Structural Proteomics, Best Institute, 112 College St., Toronto, Ontario, M5G1L6 Canada.
John R
JR
Walker
Svetlana
S
Altamentova
Alexandra
A
Ezersky
Graciela
G
Lorca
Tatiana
T
Skarina
Marina
M
Kudritska
Linda J
LJ
Ball
Alexey
A
Bochkarev
Alexei
A
Savchenko
D000481:Allantoin / Q000737:chemistry* / Q000378:metabolism*; D000595:Amino Acid Sequence; D001665:Binding Sites; D004926:Escherichia coli / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006038:Glyoxylates / Q000737:chemistry* / Q000378:metabolism; D008024:Ligands; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D012097:Repressor Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D040681:Structural Homology, Protein; D013379:Substrate Specificity
C510361:AllR protein, E coli; D029968:Escherichia coli Proteins; D006038:Glyoxylates; D008024:Ligands; D012097:Repressor Proteins; D000481:Allantoin; C031150:glyoxylic acid