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2.A.3.8.19
B(0,+)-type amino acid transporter 1 (B(0,+)AT) (Glycoprotein-associated amino acid transporter b0,+AT1) (Solute carrier family 7 member 9).  The cryo-EM structure of the human heteromeric amino acid transporter b(0,+)AT-rBAT complex has been solved (Yan et al. 2020). The two subunits, a heavy chain and a light chain are linked by a disulfide bridge. The light chain forms a heterodimer with rBAT, a heavy chain which mediates the membrane trafficking of b(0,+)AT. The b(0,+)AT-rBAT complex is an obligatory exchanger, which mediates the influx of cystine and cationic amino acids and the efflux of neutral amino acids in the kidney and small intestine. Yan et al. 2020 reported the cryo-EM structure of the human b(0,+)AT-rBAT complex alone and in complex with an arginine substrate at resolutions of 2.7 and 2.3 Å, respectively. The overall structure is a dimer of heterodimers. Arg is bound to the substrate binding site in an occluded pocket. The cryoEM structure reveals a heterotetrameric protein assembly composed of two heavy and two light chain subunits, respectively. The  interaction between the two units is mediated by dimerization of the heavy chain subunits and does not include participation of the light chain subunits (Wu et al. 2020). The b((0,+))AT1 transporter adopts a LeuT fold and is in an inward-facing conformation. An amino-acid-binding pocket is formed by transmembrane helices 1, 6, and 10 and is conserved among SLC7 transporters.

Accession Number:P82251
Protein Name:B(0,+)-type amino acid transporter 1
Length:487
Molecular Weight:53481.00
Species:Homo sapiens (Human) [9606]
Number of TMSs:12
Location1 / Topology2 / Orientation3: Membrane1 / Multi-pass membrane protein2
Substrate Amino acids

Cross database links:

Entrez Gene ID: 11136   
KEGG: hsa:11136   

Gene Ontology

GO:0005887 C:integral to plasma membrane
GO:0015184 F:L-cystine transmembrane transporter activity
GO:0015175 F:neutral amino acid transmembrane transporter activity
GO:0042605 F:peptide antigen binding
GO:0007596 P:blood coagulation
GO:0006520 P:cellular amino acid metabolic process
GO:0006811 P:ion transport
GO:0050900 P:leukocyte migration
GO:0006461 P:protein complex assembly

References (9)

[1] “Non-type I cystinuria caused by mutations in SLC7A9, encoding a subunit (b0,+AT) of rBAT.”  Feliubadalo L.et.al.   10471498
[2] “Luminal heterodimeric amino acid transporter defective in cystinuria.”  Pfeiffer R.et.al.   10588648
[3] “Human cystinuria-related transporter: localization and functional characterization.”  Mizoguchi K.et.al.   11318953
[4] “SLC7A9 mutations in all three cystinuria subtypes.”  Leclerc D.et.al.   12371955
[5] “Complete sequencing and characterization of 21,243 full-length human cDNAs.”  Ota T.et.al.   14702039
[6] “The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC).”  The MGC Project Teamet.al.   15489334
[7] “Functional analysis of mutations in SLC7A9, and genotype-phenotype correlation in non-type I cystinuria.”  Font M.et.al.   11157794
[8] “Cystinuria in children: distribution and frequencies of mutations in the SLC3A1 and SLC7A9 genes.”  Botzenhart E.et.al.   12234283
[9] “Mutation analysis of SLC7A9 in cystinuria patients in Sweden.”  Harnevik L.et.al.   12820697
Structure:
6LI9   6LID     

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Predict TMSs (Predict number of transmembrane segments)
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FASTA formatted sequence
1:	MGDTGLRKRR EDEKSIQSQE PKTTSLQKEL GLISGISIIV GTIIGSGIFV SPKSVLSNTE 
61:	AVGPCLIIWA ACGVLATLGA LCFAELGTMI TKSGGEYPYL MEAYGPIPAY LFSWASLIVI 
121:	KPTSFAIICL SFSEYVCAPF YVGCKPPQIV VKCLAAAAIL FISTVNSLSV RLGSYVQNIF 
181:	TAAKLVIVAI IIISGLVLLA QGNTKNFDNS FEGAQLSVGA ISLAFYNGLW AYDGWNQLNY 
241:	ITEELRNPYR NLPLAIIIGI PLVTACYILM NVSYFTVMTA TELLQSQAVA VTFGDRVLYP 
301:	ASWIVPLFVA FSTIGAANGT CFTAGRLIYV AGREGHMLKV LSYISVRRLT PAPAIIFYGI 
361:	IATIYIIPGD INSLVNYFSF AAWLFYGLTI LGLIVMRFTR KELERPIKVP VVIPVLMTLI 
421:	SVFLVLAPII SKPTWEYLYC VLFILSGLLF YFLFVHYKFG WAQKISKPIT MHLQMLMEVV 
481:	PPEEDPE