Cloning and characterization of MgtE, a putative new class of Mg2+ transporter from Bacillus firmus OF4.
The MM281 strain of Salmonella typhimurium which possesses mutations in each its three known Mg2+ transport systems and requires 100 mM Mg2+ for growth was used to screen a genomic library from the gram-positive alkaliphilic bacterium Bacillus firmus OF4 for clones that could restore the ability to grow without Mg2+ supplementation. Of the clones obtained, five also conferred sensitivity to Co2+, similar to the phenotype of mutants with mutations in the S. typhimurium corA Mg2+ transport locus. All five contained identical inserts by restriction analysis. Using 63Ni2+ as a surrogate for the unavailable 28Mg2+, the plasmid insert was shown to restore cation uptake with properties similar but not identical to those of the S. typhimurium CorA Mg2+ transporter. Sequence analysis of one clone identified a single open reading frame with multiple possible initiation sites. Deletion and mutation analysis identified a minimum open reading frame of 939 bp encoding a polypeptide with a predicted molecular mass of 34 kDa. Disruption of the open reading frame eliminated cation influx activity and restored resistance to Co2+. This putative transporter, designated MgtE, has no sequence similarity to any known protein including CorA and appears to represent a new class of Mg2+ transport system.
Smith
R L
RL
Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106-4965.
Thompson
L J
LJ
Maguire
M E
ME
D000595:Amino Acid Sequence; D017920:Antiporters / Q000235:genetics* / Q000378:metabolism; D001407:Bacillus / Q000235:genetics*; D001426:Bacterial Proteins; D001483:Base Sequence; D001692:Biological Transport; D002352:Carrier Proteins / Q000235:genetics; D027682:Cation Transport Proteins; D002413:Cations, Divalent / Q000378:metabolism; D003035:Cobalt / Q000378:metabolism; D005798:Genes, Bacterial / Q000235:genetics*; D005816:Genetic Complementation Test; D015698:Genomic Library; D008274:Magnesium / Q000378:metabolism*; D008969:Molecular Sequence Data; D009532:Nickel / Q000378:metabolism; D016366:Open Reading Frames; D010641:Phenotype; D011487:Protein Conformation; D012486:Salmonella typhimurium; D017422:Sequence Analysis, DNA
D017920:Antiporters; D001426:Bacterial Proteins; D002352:Carrier Proteins; D027682:Cation Transport Proteins; D002413:Cations, Divalent; C072716:CorA protein, Salmonella; C092192:MgtE protein, bacteria; D003035:Cobalt; D009532:Nickel; D008274:Magnesium