This group dissipated from the ECF classification during the reclassification by [[Casas-Pastor et al.]]!

Taxonomical distribution

ECF σ factors of group ECF13 were found exclusively in Proteobacteria (Staroń et al., 2009).

Experimentally studied examples

The Ecf protein of Neisseria gonorrhoeae (Gunesekere et al., 2006) belongs to the ECF13 group and was already experimentally addressed.

Genomic context conservation

There is no genomic context conservation beyond the co-transcribed gene encoding the anti-σ factor (Staroń et al., 2009).

Signaling mechanism

The small soluble anti-σ factors of group ECF13 also contain an N-terminal ZAS domain (Staroń et al., 2009). Binding of Zn2+ to this domain is determined by the redox state of coordinating cysteine residues and imposes conformational changes in the protein (Zdanowski et al., 2006) that ultimately determine the binding or release of the σ factor.

Physiological function

ECF13 σ factors are presumably also involved in oxidative stress responses (Gunesekere et al., 2006).


Members of original ECF13 are present in new ECF293, together with members of original ECF101 and ECF117. 43.98% of the proteins of ECF293 have homology to original ECF13.


Gunesekere IC, Kahler CM, Ryan CS, Snyder LAS, Saunders NJ, et al. 2006. Ecf, an alternative sigma factor from Neisseria gonorrhoeae, controls expression of msrAB, which encodes methionine sulfoxide reductase. Journal of Bacteriology 188 (10): 3463–3469.
Staroń A, Sofia HJ, Dietrich S, Ulrich LE, Liesegang H, et al. 2009. The third pillar of bacterial signal transduction: classification of the extracytoplasmic function (ECF) sigma factor protein family. Molecular Microbiology 74 (3): 557–581.
Zdanowski K, Doughty P, Jakimowicz P, O’Hara L, Buttner MJ, et al. 2006. Assignment of the zinc ligands in RsrA, a redox-sensing ZAS protein from Streptomyces coelicolor. Biochemistry 45 (27): 8294–8300.
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