The LytTR ('litter') HTH domain is a DNA-binding, potential winged helix-turn-helix (wHTH) domain of about 100 amino acids, present in bacterial transcriptional regulators of the algR/agrA/lytR family. It is named after Bacillus subtilis LytT and Staphylococcus aureus lytR response regulators, involved in the regulation of cell autolysis [1]. The LytTR domain is found in several bacterial cytoplasmic proteins that regulate the production of important virulence factors, like extracellular polysaccharides, toxins and bacteriocins. These response regulators of the microbial two-component signal transduction systems contain N-terminal cheY-like domains (see <PDOC50110>) and the LytTR domain in the C-terminal part is expected to bind to specific DNA sequences in the upstream regions of target genes [2]. Other domains found N-terminally of LytTR are an ATP-binding domain of ABC-type transporter family (see <PDOC00185>) and a PAS domain (see <PDOC50112>). Besides these cytoplasmic proteins, LytTR also occurs in membrane-bound bacterial proteins. The N-terminal parts of these proteins contain three to eight predicted transmembrane segments or the transmembrane MHYT domain (see <PDOC50924>).

According to secondary structure predictions the LytTR domain consists of four β-strands and three α-helices. The structure is predicted to form a novel type of DNA-binding domain, showing similarity to the 'winged HTH' or 'winged helix' proteins [1,2].

Some cytoplasmic proteins known to contain a LytTR domain:

• Pseudomonas aeruginosa algR, a transcriptional regulator involved in the pathogenesis of cystic fibrosis, in the regulation of alginate biosynthesis and twitching motility.
• Clostridium perfringens virR, involved in the pathogenesis of gas gangrene as a regulator of virulence factors such as perfringolysin O, collagenase, hemagglutinin.
• Staphylococcus aureus agrA and lytR, regulators of virulence factors and peptidoglycan turnover. AgrA is involved in the pathogenesis of toxic shock syndrome as a quorum-sensing regulator of expression of toxins, hemolysins and other virulence factors.
• Klepsiella pneumoniae mrkE, a regulator of fimbrial expression.
• Streptococcus pneumoniae comE and blpR, quorum-sensing autocatalytical response regulators of competence and of bacteriocin-like peptide production essential for survival, respectively.
• Escherichia coli mrkE and yehT.
• Bacillus subtilis lytT.

Some membrane-bound proteins known to contain a LytTR domain:

• Oligotropha carboxidovorans coxC and coxH.
• Xanthomonas campestris rpfD.
• Caulobacter crescentus CC0295, CC0330, CC0551, CC1610 and CC3036.

The profile we developed covers the entire LytTR domain.