TABLE 1.

Functional roles of substrate capture components of ECF transporters

Transporter	Pfam accession no.a	Substrateb	Evidence for specificityc	Evidence for AT module dependenced	Reference(s) and/or sourcee
BioY	PF02632	Biotin	E, R, C, O	E, C, O	14, 27, 28, 31
NikMN	PF01891	Nickel	E, R, C	E, C	29
CbiMN	PF01891	Cobalt	E, R, C	E, C	29, 33
YkoE		Thiamine precursors (HMP?)	R, C	C	34
MtsT	PF07155	Methionine precursors	R, C	C	32
HtsT	PF09605	?		C, O
QrtT		Queuosine precursor	R, C, O	C, O
CbrT		Cobalamin precursor	C, O	C, O
MtaT		Methylthioadenosine	C	C
RibU		Riboflavin	E, R, O	E, C, O	2, 5, 10, 21, 42, 43; this study
FolT		Folate	E, C, O	E, O	This study
QueT	PF06177	Queuosine precursor	R	C, O
PanT		Pantothenate	C, O	E, C, O	This study
HmpT		Thiamine precursor (HMP?)	C, O	C, O
ThiT	PF09515	Thiamine	E, R, O	E, O	7, 34; this study
ThiW		Thiazole	R, C, O	C, O	34
NiaX		Niacin	R, O	O	30
TrpP		Tryptophan	E, R	E, C, O	37, 41
PdxT		Pyridoxine	C	O
CblT		Cobalamin precursor (DMB?)	R, C, O	C, O	33
LipT		Lipoate	C	O

^aIdentifiers of protein families are from the Pfam database (http://pfam.sanger.ac.uk/) (8).

^bHMP, hydroxymethylpyrimidine; DMB, dimethylbenzimidazole.

^cEvidences for the function of S components include experimental analysis (E), coregulation of their genes in a regulon (R), colocalization on the chromosome (C), or cooccurrence (O) in the genome with metabolic genes from the same pathway.

^dEvidences for the AT module dependence of S components. E, experimental; C, colocalization on the chromosome (C), or cooccurrence (O) in the genome with AT module gene cassettes.

^eReferences describing genomic predictions and experimental validations are in italics and in bold, respectively.