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

Taxonomical distribution

ECF34 σ factors are present predominately in organisms of the phylum Cyanobacteria, but can occasionally be found in organisms belonging to other phyla, such as Acidobacteria, Actinobacteria, Chloroflexi and Proteobacteria (Staroń et al., 2009).

Experimentally studied examples


Genomic context conservation

As in many other groups, the genomic context conservation does not extend beyond the genes encoding the σ factor and its cognate membrane-associated anti-σ factor, which contain an N-terminal CAS domain and C-terminal RskA domain (Staroń et al., 2009).

Signaling mechanism


Physiological function



Members of original group ECF34 are merged in new group ECF19. 2.72% of the proteins from new ECF19 have homology to original ECF34.


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.
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