Summary:
RutR regulates genes directly or indirectly involved in the complex pathway of pyrimidine metabolism [1, 6] and also plays a role in regulation of the genes for degradation of purines and genes for maintenance of pH homeostasis [1].
This protein belongs to the TetR family, whose members have an N-terminal DNA-binding domain that contains a helix-turn-helix motif and a C-terminal domain for dimerization and ligand binding [7].
RutR recognizes and binds a 16-bp (7-2-7) inverted repeat consensus sequence [1, 2], where the central A/T nucleotide in each half-site appears to be the most important for the site [2]. This binding is inhibited when uracil and thymine bind to RutR, although the effect is greater for uracil than for thymine [1].
Based on the crystal structure of an unliganded mutant RutR protein, a structural basis for the use of uracil as the sole effector molecule was determined
[4]. RutR shows a binding site that is rich in aromatic and hydrophobic residues
[4]. Tryptophan residues W77 and W167 and the hydrophobic leucine residue L74 play an important role in binding of the planar ring-shaped uracil molecule that abolishes the DNA-binding capacity of the regulator. Residue L78 plays a crucial role in determining the effector specificity of RutR
[4].
It has been demonstrated, in
E. coli as in other bacteria, that RutR binds to several coding regions located hundreds of base pairs downstream of the start codon. However, no role in transcriptional regulation of this binding has been observed
[2].
In an experiment using directed cell evolution of a Δ
panD mutant (containing a damaged CoA biosynthesis pathway), a pathway for β-alanine biosynthesis via uracil degradation emerged. One of the required mutations is an L55P change in RutR. This mutation enables derepression of the |FRAME: PWY0-1471| pathway and eventual production of β-alanine from the pathway intermediate malonic semialdehyde
[8].
The
rutR gene, which is autorepressed
[1], is transcribed divergently from the RutR-regulated
rutABCDEFG operon
[6].
RutR: "py
rimidine
utilization, rut
repressor"
[6]
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