PFAM accession number:PF03472
Interpro abstract (IPR005143):

This domain binds N-acyl homoserine lactones (AHLs), which are also known as autoinducers. These are small, diffusible molecules used as communication signals in a large variety of proteobacteria. It is almost always found in association with the DNA-binding LuxR domain ( IPR000792 ). The autoinducer binding domain forms the N-terminal region of the protein, while the DNA-binding domain forms the C-terminal region. In most cases, binding of AHL by this N-terminal domain leads to unmasking of the DNA-binding domain, allowing it to bind DNA and activate transcription [ (PUBMED:11544353) ]. In rare cases, some LuxR proteins such as EsaR, act as repressors [ (PUBMED:12067349) ]. In these proteins binding of AHL to this domain leads to inactivation of the protein as a transcriptional regulator. A large number of processes have been shown to be regulated by LuxR proteins, including bioluminescence, production of virulence factors in plant and animal pathogens, antibiotic production and plasmid transfer.

Structural studies of TraR from Agrobacterium tumefaciens [ (PUBMED:12087407) (PUBMED:12198141) ] show that the functional protein is a homodimer. Binding of the cognate AHL is required for protein folding, resistance to proteases and dimerisation. The autoinducer binding domain binds its cognate AHL in an alpha/beta/alpha sandwich and provides an extensive dimerisation surface, though residues from the C-terminal region also make some contribution to dimerisation. The autoinducer binding domain is also required for interaction with RpoA, allowing transcription to occur [ (PUBMED:15237104) ].

There are some proteins which consist solely of the autoinducer binding domain. The function of these is not known, but TrlR from Agrobacterium has been shown to inhibit the activity of TraR by the formation of inactive heterodimers [ (PUBMED:11309123) ].

This is a PFAM domain. For full annotation and more information, please see the PFAM entry Autoind_bind