Degen O, Kobayashi M, Shimizu S, Eitinger T
Humboldt-Universität zu Berlin, Institut für Biologie/Mikrobiologie, Germany.
Arch Microbiol. 1999 Feb;171(3):139-45. doi: 10.1007/s002030050691.
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.
nhlF基因和hoxN基因分别编码红平红球菌J1的钴转运蛋白和嗜碱产碱杆菌H16的镍通透酶，它们在大肠杆菌中表达。通过先前描述的生理学检测方法检测重组体对(^{57}Co^{2 +})和(^{63}Ni^{2 +})的转运。尽管这些转运蛋白高度相似，但观察到它们对二价过渡金属阳离子有不同的偏好。HoxN不能转运(^{57}Co^{2 +})，但介导(^{63}Ni^{2 +})的摄取。后一种活性不受十倍过量的其他二价阳离子的影响，表明HoxN对(Ni^{2 +})具有特异性。相比之下，NhlF既能转运(^{57}Co^{2 +})也能转运(^{63}Ni^{2 +})离子。在存在(Co^{2 +})的情况下，NhlF介导的(^{63}Ni^{2 +})摄取明显减少，而在存在(Ni^{2 +})的情况下，(^{57}Co^{2 +})摄取仅略有降低。这些结果表明NhlF对(Co^{2 +})和(Ni^{2 +})具有不同的亲和力，并确定(Co^{2 +})离子为首选底物。
