Table 1. Amino acid sequences of the conserved anion selectivity filter region of several EriCs.

Eight EriCs (dotted box) were shown to be involved in fluoride resistance [14, 21]. Solid boxes show the amino acid sequences associated with fluoride resistance. Related EriCs commonly contain a specific set of amino acids, which are distinct from validated chloride-specific EriCs.

Substrate	Organism	Cl− selectivity filter residues
Cl−	human (ClC-1)	GSGIP……GKEGP……GGFMP……Y
Cl−	Escherichia coli	GSGIP……GREGP……GIFAP……Y
Cl−	Salmonella typhimurium	GSGIP……GREGP……GIFAP……Y
F−	Pseudomonas syringae	GNNLI……GREGT……GEVTP……Y
F−	Pirellula staleyi	GNNLL……GREGT……GEVTP……Y
F−	Ralstonia picketti	GNNLL……GREGT……GEVTP……Y
F−	Clostridium difficile	GMNLI……GREGV……GEVTP……Y
F−	Eubacterium ventriosum	GMNLV……GREGV……GEVTP……Y
F−	Lactococcus lactis	GMGLI……GREGV……GEVTP……Y
F−	Streptococcus mutans	GMGLI……GREGV……GEVTP……Y
F−	Streptococcus anginosus	GMTLI……GREGV……GEVTP……Y
F−	Streptococcus sobrinus	GMGLV……GREGV……GEVTP……Y
F−	Streptococcus australis	GMELL……GREGV……GEVTP……Y
F−	Streptococcus parasanguinis	GMGLI……GREGV……GEVTP……Y
F−	Streptococcus salivarius	GMGLI……GREGV……GEVTP……Y
F−	Streptococcus vestibularis	GMGLI……GREGV……GEVTP……Y
F−	Streptococcus constellatus	GMTLI……GREGV……GEVTP……Y
F−	Streptococcus intermedius	GMTLI……GREGV……GEVTP……Y