>TIGR01728 SsuA_fam ABC transporter, substrate-binding protein, aliphatic sulfonates family; InterPro: IPR010067 ABC transporters belong to the ATP-Binding Cassette (ABC) superfamily, which uses the hydrolysis of ATP to energize diverse biological systems. ABC transporters are minimally constituted of two conserved regions: a highly conserved ATP binding cassette (ABC) and a less conserved transmembrane domain (TMD). These regions can be found on the same protein or on two different ones. Most ABC transporters function as a dimer and therefore are constituted of four domains, two ABC modules and two TMDs. ABC transporters are involved in the export or import of a wide variety of substrates ranging from small ions to macromolecules. The major function of ABC import systems is to provide essential nutrients to bacteria. They are found only in prokaryotes and their four constitutive domains are usually encoded by independent polypeptides (two ABC proteins and two TMD proteins). Prokaryotic importers require additional extracytoplasmic binding proteins (one or more per systems) for function. In contrast, export systems are involved in the extrusion of noxious substances, the export of extracellular toxins and the targeting of membrane components. They are found in all living organisms and in general the TMD is fused to the ABC module in a variety of combinations. Some eukaryotic exporters encode the four domains on the same polypeptide chain . The ABC module (approximately two hundred amino acid residues) is known to bind and hydrolyze ATP, thereby coupling transport to ATP hydrolysis in a large number of biological processes. The cassette is duplicated in several subfamilies. Its primary sequence is highly conserved, displaying a typical phosphate-binding loop: Walker A, and a magnesium binding site: Walker B. Besides these two regions, three other conserved motifs are present in the ABC cassette: the switch region which contains a histidine loop, postulated to polarize the attaching water molecule for hydrolysis, the signature conserved motif (LSGGQ) specific to the ABC transporter, and the Q-motif (between Walker A and the signature), which interacts with the gamma phosphate through a water bond. The Walker A, Walker B, Q-loop and switch region form the nucleotide binding site , , . The 3D structure of a monomeric ABC module adopts a stubby L-shape with two distinct arms. ArmI (mainly beta-strand) contains Walker A and Walker B. The important residues for ATP hydrolysis and/or binding are located in the P-loop. The ATP-binding pocket is located at the extremity of armI. The perpendicular armII contains mostly the alpha helical subdomain with the signature motif. It only seems to be required for structural integrity of the ABC module. ArmII is in direct contact with the TMD. The hinge between armI and armII contains both the histidine loop and the Q-loop, making contact with the gamma phosphate of the ATP molecule. ATP hydrolysis leads to a conformational change that could facilitate ADP release. In the dimer the two ABC cassettes contact each other through hydrophobic interactions at the antiparallel beta-sheet of armI by a two-fold axis , , , , , . Proteins known to belong to this family are classified in several functional subfamilies depending on the substrate used (for further information see http://www.tcdb.org/tcdb/index.php?tc=3.A.1). Members of this family are substrate-binding periplasmic proteins of ABC transporters. This subfamily includes SsuA, a member of a transporter operon needed to obtain sulphur from aliphatic sulphonates. Related proteins include taurine (NH2-CH2-CH2-S03H) binding proteins, the probable sulphate ester binding protein AtsR, and the probable aromatic sulphonate binding protein AsfC. All these families make sulphur available when Cys and sulphate levels are low.; GO: 0006790 sulfur metabolic process, 0006810 transport, 0016020 membrane.

Probab=95.93  E-value=0.024  Score=34.17  Aligned_cols=134  Identities=19%  Similarity=0.107  Sum_probs=80.8

Q ss_pred             EHHHHHHHCCCCCCCCCCC-HHHHHHHHHCCCCCCCH-HC--CCCHHHHHH-HCCC----CCCCCCCCCCCCCCCCCCCC
Q ss_conf             1678997629985556689-88988643103221100-00--367567542-0023----33222222222111222211
Q gi|254781112|r   72 LIKEVAHRLNLKVEFFETA-VSGLITGLDTNRYDVLV-NV--AITPERQKK-YDFS----IPYIAHRVLLVVRSDQQDIR  142 (274)
Q Consensus        72 l~~~i~~~lg~~~~~~~~~-~~~~~~~l~~g~~D~~~-~~--~~t~eR~~~-~~fs----~p~~~~~~~~~~~~~~~~~~  142 (274)
T Consensus        22 ~~~~~~~~~g~~~~~~~f~~g~~~~~~l~~g~~d~g~~g~~p~~~~~-~~g~~~~~~~~~~~~~~~~~~~~~~~~-~~i~   99 (311)
T TIGR01728        22 LLEKEGGKEGTKVEWVEFPGGPPELEALGAGSLDFGYIGPGPALNAY-AAGNADIKAVGLSSDGPSATALVVGKG-SGIR   99 (311)
T ss_pred             HHHHCCCCCCCEEEEEEECCCHHHHHHHCCCCCCCCCCCCCHHEEEC-CCCCCCEEEEEEECCCCCCEEEEECCC-CCCC
T ss_conf             13440365661247886267547777520565001433673120100-036764679985257764035663366-7730


Q ss_pred             CCCCCCCCCEEEECCCHHHHHH----HCCC------C----CCEEECCHHHHHHHHHHHHHHCCCCCHHHHHHHHHHCC
Q ss_conf             1112334320231010122332----0134------5----42133685577775544321003665589999998458
Q gi|254781112|r  143 SFKDLTDKTVAQILGTDLSRFA----KELK------S----HLVFSHNFEQSLQLLLSKRTDATMIPDIPFFNFLERRP  207 (274)
Q Consensus       143 ~~~dL~g~~V~~~~g~~~~~~l----~~~~------~----~~~~~~~~~~~~~~l~~grvD~~~~~~~~~~~~~~~~~  207 (274)
T Consensus       100 ~~~dlkGk~~a~~~g~~~~~~~~~~l~~~ggl~~~~~~~~d~~~~~~~~~~~~~a~~~g~~da~~~~~P~~~~~~~~~~  178 (311)
T TIGR01728       100 SVKDLKGKRIAVPKGGSGHDLLLRALLKAGGLEDNLLSGDDVDILELGPSDARAALAAGQVDAWGIWEPWLSALVEEGG  178 (311)
T ss_pred             HHHHCCCCEEEEECCCCHHHHHHHHHHHHCCCCCCCCCCCCEEEEECCCHHHHHHHHCCCCCEEECCCCCHHHHHHHCC
T ss_conf             1433477456630666157899999997347200036876315540260456776540462212116871445432226