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J. Bacteriol., Apr 1995, 1840-1843, Vol 177, No. 7
L Wolfram, B Friedrich and T Eitinger
HoxN, an integral membrane protein with seven transmembrane helices and a
molecular mass of 33.1 kDa, is involved in high-affinity nickel transport
in Alcaligenes eutrophus H16. From genetic analyses, it has been concluded
that HoxN is a single-component ion carrier. To investigate this
assumption, hoxN was introduced into Escherichia coli. The recombinant
strain showed significantly enhanced nickel uptake in a short-interval
assay. Likewise, growth in the presence of 63NiCl2 yielded a more than
15-fold-increased cellular nickel content. The HoxN- based nickel transport
activity could also be demonstrated in a physiological assay: an E. coli
strain coexpressing hoxN and the urease operon of Klebsiella aerogenes
exhibited urease activity 10-fold greater than that in the strain lacking a
functional hoxN. These results strongly suggest that HoxN is sufficient to
operate as a nickel permease. Multiple sequence alignment of HoxN and four
other bacterial membrane proteins implicated in nickel metabolism revealed
two conserved signatures which may play a role in the nickel translocation
process.
Copyright © 1995, American Society for Microbiology
The Alcaligenes eutrophus protein HoxN mediates nickel transport in Escherichia coli
Institute fur Biologie, Humboldt-Universitat zu Berlin, Germany.
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