Projection structure of a member of the amino acid/polyamine/organocation transporter superfamily.
The L-arginine/agmatine antiporter AdiC is a key component of the arginine-dependent extreme acid resistance system of Escherichia coli. Phylogenetic analysis indicated that AdiC belongs to the amino acid/polyamine/organocation (APC) transporter superfamily having sequence identities of 15-17% to eukaryotic and human APC transporters. For functional and structural characterization, we cloned, overexpressed, and purified wild-type AdiC and the point mutant AdiC-W293L, which is unable to bind and consequently transport L-arginine. Purified detergent-solubilized AdiC particles were dimeric. Reconstitution experiments yielded two-dimensional crystals of AdiC-W293L diffracting beyond 6 angstroms resolution from which we determined the projection structure at 6.5 angstroms resolution. The projection map showed 10-12 density peaks per monomer and suggested mainly tilted helices with the exception of one distinct perpendicular membrane spanning alpha-helix. Comparison of AdiC-W293L with the projection map of the oxalate/formate antiporter from Oxalobacter formigenes, a member from the major facilitator superfamily, indicated different structures. Thus, two-dimensional crystals of AdiC-W293L yielded the first detailed view of a transport protein from the APC superfamily at sub-nanometer resolution.
Casagrande
Fabio
F
M. E. Müller Institute for Structural Biology, Biozentrum of the University of Basel, CH-4056 Basel, Switzerland.
Ratera
Merce
M
Schenk
Andreas D
AD
Chami
Mohamed
M
Valencia
Eva
E
Lopez
Jesus Maria
JM
Torrents
David
D
Engel
Andreas
A
Palacin
Manuel
M
Fotiadis
Dimitrios
D
D026905:Amino Acid Transport Systems / Q000737:chemistry* / Q000235:genetics; D026923:Amino Acid Transport Systems, Basic / Q000737:chemistry* / Q000235:genetics; D000818:Animals; D017920:Antiporters / Q000737:chemistry* / Q000235:genetics; D018360:Crystallography, X-Ray / Q000379:methods; D019281:Dimerization; D004926:Escherichia coli / Q000737:chemistry* / Q000235:genetics; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics; D006801:Humans; D020624:Oxalobacter formigenes / Q000737:chemistry / Q000235:genetics; D010802:Phylogeny; D020836:Protein Structure, Quaternary / Q000502:physiology
C476528:AdiC protein, E coli; D026905:Amino Acid Transport Systems; D026923:Amino Acid Transport Systems, Basic; D017920:Antiporters; D029968:Escherichia coli Proteins