LrhA, LysR homologue A, regulates the transcription of genes involved in the synthesis of type 1 fimbriae . Indirectly, this protein also regulates the transcription of several genes involved in motility, chemotaxis, and flagellum synthesis by directly controlling the expression of the master regulator FlhDC .
On the other hand, LrhA also regulates negatively and partially the translation of rpoS through two mechanisms, one of which is RprA dependent and the other one is RprA independent. RprA is a small RNA that regulates positively the translation of rpoS. Both mechanisms of regulation require the presence of the sRNA chaperone Hfq; therefore, it was suggested that another small RNA, in addition to RprA, that regulates rpoS translation is regulated by LrhA .
LrhA is a protein that belongs to the LysR family and, like the members of this family, LrhA contains three different domains: an N-terminal helix-turn-helix domain for DNA binding, a coinducer recognition domain in the center of the protein, and a C-terminal domain that contains a cluster of four cysteine and two histidine residues .
The activity of most members of this family is controlled by small molecules; however, the effector of LrhA was not known until now . LrhA has high degree of homology to HexA from Erwinia carotovora (64% identity) and PecT from Erwinia chrysanthemi (61% identity) [5, 6].Read more >
LrhA appears to recognize and bind to a partial palindromic DNA sequence of 13 bp that shows low similarity to the general consensus for LysR family members .
The lrhA gene is transcribed alone, and it is under positive autoregulation by LrhA. Unlike the majority of LysR-type regulators, LrhA does not regulate the expression of adjacent genes to lrhA . The expression of lrhA is repressed by the RcsCDB phosphorelay system and by the DNA motor protein FtsK .
|Connectivity class:||Local Regulator|
|Length:||939 bp / 312 aa|
|TU(s) encoding the TF:||
|Regulated gene(s)||fimE, flhC, flhD, lrhA|
|Multifun term(s) of regulated gene(s)||
MultiFun Term (List of genes associated to the multifun term)
fimE, flhC, flhD, lrhA
Transcription related (3)
flhC, flhD, lrhA
flhC, flhD, lrhA
motility, chemotaxis, energytaxis (aerotaxis, redoxtaxis etc) (2)
fimbri, pili (1)
DNA recombination (1)
DNA structure level (1)
|Regulated operon(s)||fimE, flhDC, lrhA|
|First gene in the operon(s)||fimE, flhD, lrhA|
|Simple and complex regulons|
|Simple and complex regulatory phrases||
Regulatory phrase (List of promoters regulated by the phrase)
|Functional conformation||Function||Promoter||Sigma factor||Central Rel-Pos||Distance to first Gene||Genes||Sequence||LeftPos||RightPos||Evidence (Confirmed, Strong, Weak)||References|
|Evolutionary conservation of regulatory elements|
 Blumer C., Kleefeld A., Lehnen D., Heintz M., Dobrindt U., Nagy G., Michaelis K., Emody L., Polen T., Rachel R., Wendisch VF., Unden G., 2005, Regulation of type 1 fimbriae synthesis and biofilm formation by the transcriptional regulator LrhA of Escherichia coli., Microbiology. 151(Pt 10):3287-98
 Lehnen D., Blumer C., Polen T., Wackwitz B., Wendisch VF., Unden G., 2002, LrhA as a new transcriptional key regulator of flagella, motility and chemotaxis genes in Escherichia coli., Mol Microbiol. 45(2):521-32
 Bongaerts J., Zoske S., Weidner U., Unden G., 1995, Transcriptional regulation of the proton translocating NADH dehydrogenase genes (nuoA-N) of Escherichia coli by electron acceptors, electron donors and gene regulators., Mol Microbiol. 16(3):521-34
 Harris SJ., Shih YL., Bentley SD., Salmond GP., 1998, The hexA gene of Erwinia carotovora encodes a LysR homologue and regulates motility and the expression of multiple virulence determinants., Mol Microbiol. 28(4):705-17