General description: Proteins from ECF57 have homology to original ECF57 (95.8%), are present in Planctomycetes (100%) and contain an average number of transmembrane helices of ~2 in a C-terminal extension that contains a homeodomain-like domain (8.33% of ECF57s1) and a WD40-like beta propeller repeat (21.05% of ECF57s2) as in the case of original ECF57 (Jogler et al., 2012).
Anti-σ factor: Proteins from ECF57 have a completely conserved pair of cysteine residues, one in σ2 and the other in σ4. Cysteine residues in σ4 have been found to form a disulfide bridge in the ECF SigK from Mycobacterium tuberculosis (ECF19s2) that dissociates under reducing conditions, promoting the release of the ECF from the cytoplasmic region of its AS factor, RskA (Shukla et al., 2014). This mechanism is also present in members of ECF18, such as RSPH17029_3536 from Rhodobacter sphaeroides (Coulianos, 2018).
Genomic context conservation: We found a conserved carboxypeptidase regulatory-like in ECF57s3 and tetratricopeptide repeats in the genetic context of the members of ECF57. This protein is present in the genetic context of FecI-like σ factors and ECF54 and might be part of their mechanism of regulation.
Promoter motif conservation: Predicted target promoter motifs are not conserved.
Summary: In conclusion, ECF57 is a Plactomycetal group that contains a C-terminal extension (Jogler et al., 2012) with two transmembrane helixes. The activation mechanism of members of ECF57 could involve their release from the membrane upon the onset of specific environmental cues.
Number of representative ECFs: 246
Number of non-redundant ECFs: 262
Sequences with C-terminal extension: 99.62%
Sequences with N-terminal extension: 10.31%
Overrepresented class: Planctomycetia [98.78%]
|Identification of proteins likely to be involved in morphogenesis, cell division, and signal transduction in Planctomycetes by comparative genomics.||Journal of bacteriology||2012||C. Jogler, J. Waldmann, X. Huang, M. Jogler, F. Glöckner, T. Mascher, R. Kolter||PubMed: 23002222||ECF59, ECF46, ECF57, ECF62, ECF61, ECF217, ECF58|
|Structural basis for the redox sensitivity of the Mycobacterium tuberculosis SigK-RskA σ-anti-σ complex.||Acta crystallographica. Section D, Biological crystallography||2014||J. Shukla, R. Gupta, K. Thakur, R. Gokhale, B. Gopal||PubMed: 24699647||ECF57, ECF19, ECF18, ECF288|