ECF57 ECF proteins

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.


Basic information

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%]

Sample Neighborhood

Protein WP_010049890.1 of Assembly GCF_000171775.1 (Gemmata obscuriglobus UQM 2246)

Promoter Motif


Protein sequence length distribution

Gene neighbourhood conservation analysis

Overall Pfam domain distribution: Cumulative frequency of Pfam domains across the genetic neighborhoods. Frequency is expressed as number of Pfam domains per ECF sigma factor. Only domains present in more than 75% of the neighborhoods are shown. Genetic neighborhoods contain the proteins encoded in ±10 from the ECF coding sequence. Only the non-overlapping, highest scoring domains are considered positive. If a protein contains several copies of a domain, only one instance is further considered. In order to avoid sequence bias, only proteins from assemblies defined as "representative" or "reference" by NCBI are included (see

Related publications

Title Journal Year Authors PubMed ECF groups
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
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