This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Warren, M. A. Articles by Maguire, M. E. Search for Related Content PubMed PubMed Citation Articles by Warren, M. A. Articles by Maguire, M. E.

The CorA Mg²⁺ Transporter Is a Homotetramer

Mary Ann Warren, Lisa M. Kucharski, Alexander Veenstra, Liang Shi, Paul F. Grulich, and Michael E. Maguire^*

Department of Pharmacology, Case School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106-4965

Received 2 March 2004/ Accepted 6 April 2004

CorA is a primary Mg²⁺ transporter for Bacteria and Archaea. The C-terminal domain of 80 amino acids forms three transmembrane (TM) segments, which suggests that CorA is a homo-oligomer. A Cys residue was added to the cytoplasmic C terminus (C317) of Salmonella enterica serovar Typhimurium CorA with or without mutation of the single periplasmic Cys191 to Ser; each mutant retained function. Oxidation of the Cys191Ser Cys317 CorA gave a dimer. Oxidation of Cys317 CorA showed a dimer plus an additional band, apparently cross-linked via both Cys317 and C191. To determine oligomer order, intact cells or purified membranes were treated with formaldehyde or carbon disulfide. Higher-molecular-mass bands formed, consistent with the presence of a tetramer. Cross-linking of the Bacillus subtilis CorA expressed in Salmonella serovar Typhimurium similarly indicated a tetramer. CorA periplasmic soluble domains from both Salmonella serovar Typhimurium and the archaeon Methanococcus jannaschii were purified and shown to retain structure. Formaldehyde treatment showed formation of a tetramer. Finally, previous mutagenesis of the CorA membrane domain identified six intramembrane residues forming an apparent pore that interacts with Mg²⁺ during transport. Each was mutated to Cys. In mutants carrying a single intramembrane Cys residue, spontaneous disulfide bond formation that was enhanced by oxidation with Cu(II)-1,10-phenanthroline was observed between monomers, indicating that these Mg²⁺-interacting residues within the membrane are very close to their cognate residue on another monomer. Thus, CorA appears to be a homotetramer with a TM segment of one monomer physically close to the same TM segment of another monomer.

Present address: Department of Pharmacology and Therapeutics, Roswell Park Cancer Institute, Buffalo, NY 14263.

Present address: Microbiology Group, Pacific Northwest National Laboratory, Richland, WA 99352.

This article has been cited by other articles:

• Wang, S.-Z., Chen, Y., Sun, Z.-H., Zhou, Q., Sui, S.-F. (2006). Escherichia coli CorA Periplasmic Domain Functions as a Homotetramer to Bind Substrate. J. Biol. Chem. 281: 26813-26820 [Abstract] [Full Text]  
• Eshaghi, S., Niegowski, D., Kohl, A., Molina, D. M., Lesley, S. A., Nordlund, P. (2006). Crystal Structure of a Divalent Metal Ion Transporter CorA at 2.9 Angstrom Resolution.. Science 313: 354-357 [Abstract] [Full Text]  
• Sermon, J., Wevers, E. M.-R. P., Jansen, L., De Spiegeleer, P., Vanoirbeek, K., Aertsen, A., Michiels, C. W. (2005). CorA Affects Tolerance of Escherichia coli and Salmonella enterica Serovar Typhimurium to the Lactoperoxidase Enzyme System but Not to Other Forms of Oxidative Stress. Appl. Environ. Microbiol. 71: 6515-6523 [Abstract] [Full Text]