Selective transport of divalent cations by transition metal permeases: the Alcaligenes eutrophus HoxN and the Rhodococcus rhodochrous NhlF.
nhlF and hoxN, the genes encoding a cobalt transporter of Rhodococcus rhodochrous J1 and a nickel permease of Alcaligenes eutrophus H16, respectively, were expressed in Escherichia coli. 57CO2+ and 63Ni2+ transport of the recombinants was examined by means of a previously described physiological assay. Although the transporters are highly similar, different preferences for divalent transition metal cations were observed. HoxN was unable to transport 57CO2+, but mediated 63Ni2+ uptake. The latter activity was unaffected by a tenfold excess of other divalent cations, showing the specificity of HoxN for Ni2+. In contrast, NhlF transported both 57CO2+ and 63Ni2+ ion. NhlF-mediated 63Ni2+ uptake was markedly reduced in the presence of CO2+, while 57CO2+ uptake was only slightly lower in the presence of Ni2+. These results indicate different affinities of NhlF for CO2+ and Ni2+ and identified CO2+ ion as the preferred substrate.
Degen
O
O
Humboldt-Universität zu Berlin, Institut für Biologie/Mikrobiologie, Germany.
Kobayashi
M
M
Shimizu
S
S
Eitinger
T
T
D000421:Alcaligenes / Q000235:genetics* / Q000378:metabolism; D000595:Amino Acid Sequence; D017920:Antiporters / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins; D001483:Base Sequence; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D027682:Cation Transport Proteins; D002413:Cations, Divalent / Q000378:metabolism*; D003035:Cobalt / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D017136:Ion Transport; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D009532:Nickel / Q000378:metabolism; D012240:Rhodococcus / Q000235:genetics* / Q000378:metabolism
D017920:Antiporters; D001426:Bacterial Proteins; D002352:Carrier Proteins; D027682:Cation Transport Proteins; D002413:Cations, Divalent; C089761:HoxN protein, bacteria; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; C103702:NhlF protein, Rhodococcus rhodochrous; D003035:Cobalt; D009532:Nickel