The Alcaligenes eutrophus protein HoxN mediates nickel transport in Escherichia coli.
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.
Wolfram
L
L
Institute für Biologie, Humboldt-Universität zu Berlin, Germany.
Friedrich
B
B
Eitinger
T
T
D000421:Alcaligenes / Q000737:chemistry*; D000595:Amino Acid Sequence; D017920:Antiporters / Q000737:chemistry / Q000502:physiology*; D001426:Bacterial Proteins; D001692:Biological Transport; D004926:Escherichia coli / Q000378:metabolism*; D008969:Molecular Sequence Data; D009532:Nickel / Q000493:pharmacokinetics*; D016415:Sequence Alignment; D014510:Urease / Q000378:metabolism
D017920:Antiporters; D001426:Bacterial Proteins; C089761:HoxN protein, bacteria; D009532:Nickel; D014510:Urease