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J. Bacteriol., Mar 1995, 1233-1238, Vol 177, No. 5
RL Smith, LJ Thompson and ME Maguire
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.
Copyright © 1995, American Society for Microbiology
Cloning and characterization of MgtE, a putative new class of Mg2+ transporter from Bacillus firmus OF4
Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106-4965.
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