| Type: | Family | Name: | GAF-ANTAR transcription anti-termination regulator, putative |
| Description: | Members of this group are predicted signal transduction proteins containing cytoplasmic sensor domain GAF and an RNA-binding anti-terminator ANTAR domain.In members of this group, regulation/signal receiving is predicted to be performed by the GAF domain. GAF is a ubiquitous signalling/sensory domain. It has been originally described as a non-catalytic cGMP-binding domain conserved in cyclic nucleotide phosphodiesterases []. Subsequently, this domain was recognised in cyanobacterial adenylate cyclases, histidine kinases and certain other proteins []. It has been predicted to regulate allosterically catalytic activities via binding ligands, such as nucleotides and small molecules [].ANTAR is a transcriptional anti-terminator domain [, , ] and is most often found fused to the CheY-like receiver domain to form response regulator anti-terminator (). Superficially, the coiled-coil and three-helix bundle that form this domain in AmiR [] () appear radically different from the compact HTH DNA-binding domain of the NarL protein (). However, the last three helices in AmiR are very similar in length and hydropathy profiles to those of NarL and its homologues, and are arranged in a very similar topology, suggesting an evolutionary relationship []. These C-terminal helices of AmiR appear to be essential for its transcription anti-termination activity []. However, helix-turn-helix domains like those in NarL or OmpR [] are adapted to sequence-specific binding in the major groove of double-stranded B-form DNA. It is not clear how such a structure might function in a protein whose role is to prevent the formation of a termination stem-loop structure, by binding single-stranded RNA []. | Short Name: | GAF_ANTAR |
