>TIGR01183 ntrB nitrate ABC transporter, permease protein; InterPro: IPR005889 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). This entry comprises of the nitrate transport permease in bacteria, the gene product of ntrB. The nitrate transport permease is the integral membrane component of the nitrate transport system and belongs to the ATP-binding cassette (ABC) superfamily. At least in photosynthetic bacteria nitrate assimilation is aided by other proteins derived from the operon which among others include products of ntrA, ntrB, ntrC, ntrD, narB. Functionally ntrC and ntrD resemble the ATP binding components of the binding protein-dependent transport systems. Mutational studies have shown that ntrB and ntrC are mandatory for nitrate accumulation. Nitrate reductase is encoded by narB. ; GO: 0015112 nitrate transmembrane transporter activity, 0015706 nitrate transport, 0016021 integral to membrane.

Probab=99.83  E-value=1.7e-18  Score=150.64  Aligned_cols=189  Identities=24%  Similarity=0.448  Sum_probs=176.7

Q ss_pred             HHHHHHHHHHHHHHHHHHHHHHHHHCCCCCHHHHHCHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHCCCCCCHHHHHHHH
Q ss_conf             68899999999999999999973100001124543667899985446677544469999999998315566504799999
Q gi|255764497|r  376 VLYVIWLGCITMFRVVVLIIIASIIWIPVGIWIGFRPHISSKIQPFAQLLAAFPANVFFPLVVSCVSYYHLNPNLWLSLL  455 (587)
Q Consensus       376 ~~~l~~~~~~tl~~~~~~~~~a~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ip~~~~~~~~~~~~~~~~~~~~~~~~~~  455 (587)
T Consensus        12 ~~Gl~~q~~~sl~rva~G~~~aa~~Gi~~G~~~G~~~~~~~~ldP~~q~lr~~~PlaW~Pi~l~~~~~~~----~~aifv   87 (203)
T TIGR01183        12 DKGLFLQILASLTRVAVGYLLAAIVGIAVGILIGLSKLLNKALDPIFQVLRTVPPLAWLPIALAAFQDAQ----PAAIFV   87 (203)
T ss_pred             CHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHCCHHHHHHHHHHHHCCC----CCEEEE
T ss_conf             2037999999999999999999999999999974689998742089999975153457889999984168----631311


Q ss_pred             HHHHHHHHHHHHHHHHHHHCCHHHHHHHHHCCCCHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHCCCCCCCC
Q ss_conf             99999999999999999739989999999749887899899985745778999999999999999999998505564422
Q gi|255764497|r  456 MIFGTQWYILFNVIAGASAFPNDFKEVASSFHITGWRWWRYIILPGIFPYYVTGAITACGGAWNASIVSEVASWGHIHLR  535 (587)
Q Consensus       456 ~~~~~~~~~~~~~~~gl~~i~~~l~eaa~~lGa~~~~~~~~V~LPl~~P~i~~g~~~a~~~a~~~~~~ae~~~~~~~~~~  535 (587)
T Consensus        88 ifita~WPi~int~~G~~~~P~dy~nv~rvl~ls~~~y~~~~~~P~~~Py~f~Gl~i~~Gl~Wlai~aae~~~~~-----  162 (203)
T TIGR01183        88 IFITAIWPIIINTAVGVQQIPQDYNNVARVLKLSKSDYLLKVLLPAAVPYIFTGLRIAIGLSWLAIVAAEMLIGG-----  162 (203)
T ss_pred             HHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHCC-----
T ss_conf             248779899987666676311778999999998788888877754445689865899999999999999998605-----


Q ss_pred             CCCHHHHHHHHHHHCCHHHHHHHHHHHHHHHHHHHHHH
Q ss_conf             37837999999973497989999999999999999997
Q gi|255764497|r  536 TTGLGAYIAESTEKGSFPEVVLGVLIMCCFVLALNRFL  573 (587)
Q Consensus       536 ~~GlG~~i~~~~~~~~~~~~~~~~~~~~~~~~~~~~l~  573 (587)
T Consensus       163 ~~GiGffiWday~~~~~s~~ila~~y~G~vGl~l~~~v  200 (203)
T TIGR01183       163 IVGIGFFIWDAYNSGSVSEIILAIIYVGLVGLLLDRLV  200 (203)
T ss_pred             CCHHHHHHHHHHHCCCHHHHHHHHHHHHHHHHHHHHHH
T ss_conf             43012432222301430479999999999999999998