PMID:18227061
| Citation |
Courville, P, Urbankova, E, Rensing, C, Chaloupka, R, Quick, M and Cellier, MF (2008) Solute carrier 11 cation symport requires distinct residues in transmembrane helices 1 and 6. J. Biol. Chem. 283:9651-8 |
|---|---|
| Abstract |
Ubiquitous solute carriers 11 (SLC11) contribute to metal-ion homeostasis by importing Me(2+) and H(+) into the cytoplasm. To identify residues mediating cation symport, Escherichia coli proton-dependent manganese transporter (MntH) was mutated at five SLC11-specific transmembrane (TM) sites; each mutant activity was compared with wild-type MntH, and the biochemical results were tested by homology threading. Cd(2+) and H(+) uptake kinetics were analyzed in whole cells as a function of pH and temperature, and right-side out membrane vesicles were used to detail energy requirements and to probe site accessibility by Cys replacement and thiol modification. This approach revealed that TM segment 1 (TMS1) residue Asp(34) couples H(+) and Me(2+) symport and contributes to MntH forward transport electrogenicity, whereas the TMS6 His(211) residue mediates pH-dependent Me(2+) uptake; MntH Asn(37), Asn(250), and Asn(401) in TMS1, TMS7, and TMS11 participate in transporter cycling and/or helix packing interactions. These biochemical results fit the LeuT/SLC6 structural fold, which suggests that conserved peptide motifs Asp(34)-Pro-Gly (TMS1) and Met-Pro-His(211) (TMS6) form antiparallel "TM helix/extended peptide" boundaries, lining a "pore" cavity and enabling H(+)-dependent Me(2+) import. |
| Links |
PubMed Online version:10.1074/jbc.M709906200 |
| Keywords |
Amino Acid Motifs/physiology; Amino Acids/genetics; Amino Acids/metabolism; Cadmium/metabolism; Cation Transport Proteins/genetics; Cation Transport Proteins/metabolism; Escherichia coli/genetics; Escherichia coli/metabolism; Escherichia coli Proteins/genetics; Escherichia coli Proteins/metabolism; Ion Transport/physiology; Kinetics; Protein Structure, Tertiary/physiology; Protons; Symporters/genetics; Symporters/metabolism |
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