ECF120

ECF subgroups

ECF120s1 107 ECF120s2 108 ECF120s3 106 ECF120s4 80 ECF120s5 71 ECF120s6 64 ECF120s7 77 ECF120s8 29 ECF120s9 45 ECF120s10 42 ECF120s11 18 ECF120s12 32 ECF120s13 38 ECF120s14 19 ECF120s15 27 ECF120s16 3 ECF120s17 17 ECF120s18 10 ECF120s19 15 ECF120s20 15 ECF120s21 13 ECF120s22 13 ECF120s23 6 ECF120s24 12 ECF120s25 11 ECF120s26 11 ECF120s27 20 ECF120s28 6

ECF proteins

General description: A percentage of 20.53% of the proteins from new ECF120 has homology to original ECF120. Proteins from ECF120 belong to Bacteroidetes of the orders Bacteroidales, Chitonophagales, Cytophagales, and Flavobacteriales.

Anti-σ factor: Proteins from ECF120 contain an AS factor with one TM helix in position +1 (71.22%). This AS factor usually contains either a putative zinc-finger domain or a DUF3379.

Genetic context conservation: The most conserved domain in the genetic context is DUF4252, which appears in positions +2 and +3, in some cases together with a putative auto-transporter adhesin head GIN domain (PFAM: DUF2807, with structural similarity to pectinases), in position +2 of ECF120s13, and in positions +2, -1 and -2 of ECF120s12. These proteins are soluble and might be part of the signaling mechanisms of ECF120. Members of Flavobacteriales encode a peptidase in position -1 (ECF120s2, ECF120s24, ECF120s4,  ECF120s6). Other proteins conserved are an outer membrane beta-barrel protein (+2 of ECF120s9, ECF120s7), a protein contain a 4Fe-4S dicluster domain (-1 of ECF120s15), a protein with a Cys-rich domain (-2 of ECF120s15), an amino acid kinase (-1 of ECF120s3), the pyridoxal binding domain of a pyridoxal-dependent decarboxylase (-2 of ECF120s3), a shikimate kinase (ECF120s1 and ECF120s3), a DUF45 (ECF120s3), an Holliday junction DNA helicase ruvB (ECF120s11),  a pyruvate ferredoxin/flavodoxin oxidoreductase (ECF120s13), the TPP binding domain of a thiamine pyrophosphate enzyme (ECF120s13), a putative porin (ECF120s13), a pyruvate flavodoxin/ferredoxin oxidoreductase (ECF120s13), an Adenylosuccinate lyase (ECF120s6) and a periplasmic binding protein (ECF120s4 and ECF120s6).

Studied members: One characterized member of ECF120 is PG0985 from P. gingivalis (ECF120s16). This ECF and the protein coded in +1 (inner membrane protein) and +2 (outer membrane protein with a DUF4252) are highly abundant under heme excess (Veith, Luong, Tan, Dashper, & Reynolds, 2018). Under these conditions, the PG0985 induces the expression of heme efflux pumps (Veith et al., 2018).

Promoter motif conservation: The promoter motifs are conserved and involved TGTAACAAA in -35 and TCGTCAT in -10, which suggest that they autoregulate their expression.

Summary: Given the conservation of the large amount of sensing and transport systems in the genetic context of ECF120 and the function of the only described member of this group, it is likely that ECF120 is in charge of sensing and transporting of heme and/or other metal-containing compounds, potentially from the host organisms if the bacteria is a pathogen or a commensal of mammals. ECF120 inherits the disposal of the genetic context of original ECF120 in some subgroups (Staroń et al., 2009), but extends it to other possibilities. Given the conservation of the promoter motifs, it is likely that members of ECF120 are self-regulated.