A Porter (uniporter, symporter, antiporter) 277 3 Primary active transporter 321 3.A P-P-bond hydrolysis-driven transporter 286 3.B Decarboxylation-driven ABT-737 nmr transporter 4 3.D Oxidoreduction-driven transporter 28 3.E Light absorption-driven transporter 3 4 Group translocator 7 4.A Phosphotransfer-driven group translocator 5
4.B Nicotinamide ribonucleoside uptake transporter 1 4.C Acyl CoA ligase-coupled transporter 1 5 Transmembrane electron carrier 9 5.A Transmembrane 2-electron transfer carrier 8 5.B Transmembrane 1-electron transfer carrier 1 8 Auxiliary transport proteinb 4 8.A Auxiliary transport protein 4 9 Poorly defined system 20 9.A Recognized transporter of unknown biochemical mechanism 20 Total 658 Detailed class and subclass descriptions can be found at http://www.tcdb.org. a Transporter classes 6 and 7 have not been assigned in the TC system yet and therefore are not listed here. b Auxiliary proteins facilitate transport via established transport systems and therefore are not counted as separate systems. Of the channel type proteins, almost all are alpha-type channels (Subclass 1.A), presumably in the cytoplasmic membrane. No outer membrane porins (Subclass 1.B) were identified, probably because actinobacteria have porins that differ from those in Gram-negative bacteria, and few of these have been characterized [21–25]. Those known for Mycobacteria, Nocardia
and Corynebacteria do not have homologues in Streptomyces that are selleck inhibitor sufficiently similar to be recognized. A single putative channel-forming toxin (Subclass 1.C) (belonging SPTLC1 to the BAPA Family; TCID number 1.C.42.1.1) was detected. Secondary carriers (Subclass 2.A) and primary active transporters (mostly ATP-dependent (Subclass 3.A)) represent the majority of the transporters, but a smaller percentage are decarboxylation driven (Subclass 3.B) or oxidoreduction driven (Subclass 3.D) primary active transporters. Among the seven group translocation proteins, five belong to the phosphotransferase system (Subclass 4.A), one may be a nicotinamide ribonucleoside uptake system
(Subclass 4.B), and another may be an acyl CoA ligase-coupled transporter (Subclass 4.C). Nine proteins possibly function as transmembrane electron flow carriers with eight of them carrying electron pairs (Subclass 5.A), while one may be a single electron carrier (Subclass 5.B). Substrates transported by Sco Table 2 presents numbers of transport proteins in Sco categorized according to substrate. Transporters that function with inorganic molecules as substrates can be nonselective or can exhibit selectivity toward cations or anions. Almost all nonselective transporters are channels (see Additional file 1: Table S1 and Figure 2). A large majority of cation transporters (13.9% — 89 total) are either primary active transporters (33 proteins) or secondary carriers (32 proteins).