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J. Bacteriol., May 1995, 2654-2662, Vol 177, No. 10
T Tao, MD Snavely, SG Farr and ME Maguire
Salmonella typhimurium has three distinct Mg2+ transport systems: CorA,
MgtA, and MgtB, each encoded by its respective gene. corA and mgtB have
been previously sequenced and characterized. This report details the
sequence and properties of mgtA. Like mgtB, mgtA encodes a P-type ATPase.
The mgtA gene encodes a slightly smaller protein than does mgtB, with a
predicted molecular mass of about 95 kDa, running at 91 kDa on protein
gels, which compares with values of 101 and 102 kDa, respectively, for the
MgtB protein. The deduced amino acid sequence of MgtA is only 50% identical
to that of MgtB, with a further 25% conservative amino acid substitutions,
surprisingly low for such otherwise functionally similar proteins from the
same organism. Codon usage for each gene is normal for S. typhimurium,
however, indicating that neither gene is the result of a recent acquisition
from another organism. A single open reading frame at mgtA encodes MgtA, in
contrast to mgtB, which is shown to be an operon encoding (5' to 3') the
22.5- kDa MgtC and the MgtB proteins. Genetic constructs were used to show
that deletion of MgtC does not alter the expression or transport properties
of MgtB, making the role of the companion MgtC protein unclear. (The S.
typhimurium homolog of treR, which encodes a putative repressor for
trehalose uptake, is encoded by a gene adjacent to mgtA, and its sequence
is also reported.(ABSTRACT TRUNCATED AT 250 WORDS)
Copyright © 1995, American Society for Microbiology
Magnesium transport in Salmonella typhimurium: mgtA encodes a P-type ATPase and is regulated by Mg2+ in a manner similar to that of the mgtB P-type ATPase
Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106-4965, USA.
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