>TIGR00955 3a01204 Pigment precourser permease; InterPro: IPR005284 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 family includes different parts of a membrane-spanning permease system necessary for the transport of pigment precursor into pigment cells responsible for eye color. White protein dimerises with brown protein for the transport of guanine and with scarlet protein for the transport of tryptophan.; GO: 0006810 transport.

Probab=96.80  E-value=0.0012  Score=44.18  Aligned_cols=163  Identities=20%  Similarity=0.295  Sum_probs=92.9

Q ss_pred             HHCCCCCEEEECCCCCCHHHHHHHHHHHCCCCCCE----EEEEC-CHH---------------HCCCC----CC-----E
Q ss_conf             62258848998188888889999998303876767----99964-213---------------12567----87-----5
Q gi|254780724|r  246 IGRIRCNVLISGGTGSGKTTLLNCLTRYIDKDERI----VTCED-TAE---------------LQLQQ----PH-----V  296 (483)
Q Consensus       246 ~v~~~~nilVsG~TGSGKTT~L~al~~~i~~~~ri----vtIED-~~E---------------l~l~~----~~-----~  296 (483)
T Consensus        54 ~a~~GeLlA~mGsSGAGKTTLmn~La~R~~~g~~~~g~~v~lNG~~~~~~~~~~~saYvqQ~Dlf~~~LTv~E~L~f~A~  133 (671)
T TIGR00955        54 VAKPGELLAIMGSSGAGKTTLMNALAFRSPKGLKVSGSVVLLNGRPIDAKEMRAISAYVQQDDLFIPTLTVREHLMFQAH  133 (671)
T ss_pred             EECCCEEEEEECCCCCCHHHHHHHHHCCCCCCCEECCCEEEECCEECCHHHHHHHHCHHEEHHHCCCCCCHHEEEEEEEE
T ss_conf             21067068984787662689999985337478614683678758375868998540122011004885103000010122


Q ss_pred             EEEEE---------------------------ECC---------CCCCCCCCHHHHHHHHHHHCCCCEEEECC-CCCHHH
Q ss_conf             67787---------------------------416---------66653000189999875205998899657-587999
Q gi|254780724|r  297 VRLET---------------------------RPP---------NIEGEGEITMRDLVKNCLRMRPERIILGE-VRGPEV  339 (483)
Q Consensus       297 v~~~~---------------------------~~~---------~~e~~~~~t~~~ll~~aLR~~PD~IiVGE-iRg~Ea  339 (483)
T Consensus       134 lRm~~~~~~~~~k~~rV~~vl~~l~L~~ca~T~IG~pg~~KGlSGGE-rKRLafA----~E~ltdP~~LFcDEPTSGLDS  208 (671)
T TIGR00955       134 LRMKRRVTKKHEKRERVDEVLQALGLRKCADTRIGIPGRVKGLSGGE-RKRLAFA----SELLTDPIILFCDEPTSGLDS  208 (671)
T ss_pred             EECCCCCCHHHHHHHHHHHHHHHHCCHHHHCCCCCCCCCEEEECCCH-HHHHHHH----HHHHHCCCEEEECCCCCHHHH
T ss_conf             33476676057999999999986042112113437999645520113-6789988----788718942650388953459


Q ss_pred             H---HHHH----HHHCCCCEEEHHHCCCCHHHHHHHHHHHHHHCCCCCCHHHHHHHHHHHCCEEEEEEECCCCCEEEEEE
Q ss_conf             9---9999----98739701020004788888999999755304679998999999974235889998769998789999
Q gi|254780724|r  340 L---DLLQ----AMNTGHDGSMGTIHANNARESFGRMEAMIAMGGFTLPSQMVREIITSSLDVIVQTQRLRDGSRRITNI  412 (483)
Q Consensus       340 ~---~~l~----A~~TGH~G~ltTlHa~s~~~ai~RL~~m~~~~~~~~~~~~~~~~ia~avd~iV~~~r~~dG~Rrv~~I  412 (483)
T Consensus       209 fmA~~Vv~~L~~LA~~G~t-iI~tIHQPSs~-------------------------lF~lFd~i~lla---~G-rvv---  255 (671)
T TIGR00955       209 FMAYSVVQVLKGLAQKGKT-IICTIHQPSSE-------------------------LFELFDKIILLA---EG-RVV---  255 (671)
T ss_pred             HHHHHHHHHHHHHHCCCCE-EEEEEECCCHH-------------------------HHHHHCCEEEEE---CC-EEE---
T ss_conf             9999999999998508979-99983056188-------------------------985117167752---77-279---


Q ss_pred             EEEEEEECCEEEEEEEEEEEEECCCCCCEEEE--EEEECCCCCHHHHHHHHH
Q ss_conf             99984149889986789875406688862879--999779989889999998
Q gi|254780724|r  413 CEIVGMEGNVIITQDLLKYEVMGEDETGKLIG--QHISTGVSRPRFWNRAAQ  462 (483)
Q Consensus       413 ~Ev~g~e~~~~~~~~if~~~~~~~~~~~~~~g--~~~~~g~~~~~~~~~~~~  462 (483)
T Consensus       256 -----y~G~p~~a~~FF~-----------~~Gpd~~cP~~yNPADF~~~~la  291 (671)
T TIGR00955       256 -----YLGSPDQAVPFFS-----------ELGPDFPCPENYNPADFYLQVLA  291 (671)
T ss_pred             -----EECCCHHHHHHHH-----------HCCCCCCCCCCCCCHHHHHHHHH
T ss_conf             -----8278103689898-----------44888789788888889999973