TCDB is operated by the Saier Lab Bioinformatics Group

Tripartite dicarboxylate:H+ symporter (substrates include: fumarate, D- and L-malate, succinate, succinamide, orotate, iticonate and mesaconate) (Forward et al., 1997)
DctPQM dicarboxylate transporter of Rhodobacter capsulatus
DctP (R)
DctQ (M, 4 TMS)
DctM (M, 12 TMS)

The 2,3-diketo-L-gulonate (2,3-DKG) transporter, YiaMNO [2,3-KDG is a breakdown product of L-ascorbate] (Thomas et al., 2006)
YiaMNO of E. coli
YiaM (M, 4 TMSs; most like TauL) (P37674)
YiaN (M, 12 TMSs; most like DctM) (P37675)
YiaO (R, like DctP and TauK) (P37676)

Na+-dependent (smf-driven) sialic acid (N-acetyl neuraminic acid) transporter, SiaTP (Allen et al., 2005; Severi et al., 2005; Johnston et al., 2008). SiaT is also called SiaQM (Mulligan et al., 2009).  Also transports the related sialic acids, N-glycolylneuraminic acid (Neu5Gc) and 3-keto-3-deoxy-D-glycero-D-galactonononic acid (KDN) (Hopkins et al. 2013).

SiaTP of Haemophilus influenzae
SiaT (a fusion protein equivalent to both DctM and DctQ) (616 aas; 16 TMSs) (P44543)
SiaP (R) (P44542)

Putative tripartite taurine uptake system, TauKLM (Bruggemann et al., 2004; Denger et al., 2006)

TauKLM of Rhodobacter sphaeroides
TauK (Rsph2615) (R) (Q3IVI6)
TauL (Rsph2614) (M, 4 TMS) (Q3IVI5)
TauM (Rsph2613) (M, 12 TMS) (Q3IVI4)

The putative rhamnogalacturonide transporter (Rodionov et al. 2004)

RhiABC of Salmonella typhimurium
RhiA (R) (P43020)
RhiB (M, 4 TMSs) (Q8ZKR9)
RhiC (M, 12 TMSs) (Q8ZKS0)

The Na+-dependent sialic acid uptake porter, SiaPQM. SiaQ and SiaM form a 1:1 stoichiometric complex (Mulligan et al., 2012).

SiaPQM of Vibrio cholerae
SiaP (R) (Q9KR64)
SiaQ (M, 4TMSs) (B9TSN0)
SiaM (M, 12 TMSs) (B9TSM9)

The malonate uptake transporter, MatPQM. Regulated by the GtrA transcriptional activator (Chen et al. 2010). MatM is fused in a single protein C-terminal to MatA (malonyl-CoA decarboxylase).

MatPQM of Sinorhizobium meliloti
MatP (R) (Q930W1)
MatQ (M, 4TMSs) (Q930W2)
MatM (M, 12TMSs) (Q930W3)

Sialic acid uptake transporter, DctMPQ

DctMPQ of E. coli 
DctM (Q8FA80)
DctQ (Q8FA79)
DctP (Q8FA78) 

The possible disulfide 3,3'-dithiodipropionic acid (DTDP) tripartite transporter, DctMPQ (Wübbeler et al. 2014).  More probably takes up an array of oxidized sugar onic acids, D-gluconate, D-galactonate, L-arabonate, D-fuconate and D-xylonate. The sugars are oxidized by a broad-range, membrane bound sogar oxidase.  The acids that have been studied kineticall have Kms between 8 and 15 μM (Meinert et al. 2017; ).

DTDP transporter of Advenella mimigardefordensis strain DPN7
DctM (M, large)
DctP (R)
DctQ (M, small)

Transporter for lignin derived aromatic compounds, TarPQM (Salmon et al. 2013).  The purple photosynthetic bacterium Rhodopseudomonas palustris is able to grow photoheterotrophically under anaerobic conditions on a range of phenylpropeneoid lignin monomers, including coumarate, ferulate, caffeate, and cinnamate. TarPQM is encoded at the same locus as CouPSTW (TC# 3.A.1.4.11) and several other genes involved in coumarate metabolism. The periplasmic binding-protein of this system (TarP) binds coumarate, ferulate, caffeate, and cinnamate with nanomolar KD values. Thus, R. palustris uses two redundant but energetically distinct primary and secondary transporters that both employ high-affinity periplasmic binding-proteins to maximize the uptake of lignin-derived aromatic substrates from the environment (Salmon et al. 2013).

TarPQM of Rhodopseudomonas palustris
TarP (R; 336 aas)
TarQ (small M; 217 aas)
TarM (large M; 435 aas)

Tripartite high affinity ectoine/hydroxyectoine uptake system (Grammann et al., 2002)
TeaABC ectoine transporter of Halomonas elongata
TeaA (R)
TeaB (M, 4 TMS)
TeaC (M, 12 TMS)

TRAP transporter for a hydrophobic substrate (3-d structure known; tp0958 has 18-20 TMSs) (Deka et al., 2012). The substrate could be a lipoprotein, tp0956 (O83922) which is encoded in the same operon with tp0957 and tp058. This protein differs from all other members of the TRAP-T family in having 19 predicted TMSs with extra TMSs at its N-terminus.

TRAP-T transporter of Treponema pallidum
tp0957 (R) (O83923)
tp0958 (M) (O83924) 

Tripartite glutamate:Na+ symporter (Quintero et al., 2001)
GtrABC glutamate:Na+ symporter of Synechocystis strain PCC6803
GtrA (M) (like DctQ)
GtrB (M) (like DctM)
GtrC (R) (like GlnH of E. coli)

Tripartite 4-chlorobenzoate symporter (also binds and may transport 4-bromo-, 4-iodo-, and 4-fluorobenzoate and with a lower affinity, 3-chlorobenzoate, 2-chlorobenzoate, 4-hydroxybenzoate, 3-hydroxybenzoate, and benzoate) (Chae and Zylstra, 2006)
FcbT1/T2/T3 of Comamonas sp. strain DJ-12
FcbT1 (R) (AAF16407)
FcbT2 (M-sm) (AAF16408)
FcbT3 (M-lg) (AAF16409)

The 2-oxo monocarboxylate transporter (Pernil et al., 2010). Transports pyruvate which is inhibited by various 2-ketoacids.

The 2-oxo monocarboxylate transporter of Anabaena (nostoc) sp. strain PCC7120
DctQ (Alr3026) (Q8YSQ8)
DctM (Alr3027) (Q8YSQ7)
DctP (Alr3028) (Q8YSQ6) 

The 2-ketomonocarboxylate transporter (presented in order of affinity - 2-oxovalerate [highest affinity, KD=0.1 μM], 2-oxoisovalerate, 2-oxobutyrate, 2-oxoisocaproate, 2-oxo-3-methylvalerate, pyruvate [lowest affinity, KD=3 μM]) (Thomas et al., 2006).

The 2-ketomonocarboxylate transporter of Rhodobacter capsulatus
DctM-2, M-large (D5ATK1)
DctQ-2, M-small (D5ATK0)
DctP-2, Receptor (R) (D5ALT6)