Tynecka Z, Gos Z, Zajac J
J Bacteriol. 1981 Aug;147(2):305-12. doi: 10.1128/jb.147.2.305-312.1981.
The presence of a plasmid harboring a gene for Cd2+ resistance led to markedly reduced Cd2+ uptake via the energy-dependent Mn2+ transport system in Staphylococcus aureus strain 17810R. Cd2+ uptake by the resistant strain via this high-affinity system was seen only at very low Cd2+ concentrations. At high concentrations, Cd2+ was taken up by the resistant strain via a different low-affinity uptake system. Cd2+ uptake via this system was energy dependent but was not blocked by Mn2+. Loss of the plasmid from the resistant strain resulted in Cd2+ sensitivity and unblocking of Cd2+ transport via the Mn2+ carrier in the plasmidless derivative strain 17810S. The energy-dependent Cd2+ uptake by the sensitive strain was inhibited by Mn2+ with kinetics indicating competitive inhibition. It is suggested that the second, low-affinity uptake system for Cd2+ in the resistant strain is the energy-dependent cadmium/proton antiporter, which at low Cd2+ concentrations functions in net Cd2+ efflux.
携带镉离子抗性基因的质粒的存在，导致金黄色葡萄球菌17810R菌株中通过能量依赖的锰离子转运系统摄取的镉离子显著减少。抗性菌株通过这种高亲和力系统摄取镉离子仅在非常低的镉离子浓度下可见。在高浓度下，抗性菌株通过不同的低亲和力摄取系统摄取镉离子。通过该系统摄取镉离子是能量依赖的，但不受锰离子的阻断。抗性菌株中质粒的丢失导致镉离子敏感性以及无质粒衍生菌株17810S中通过锰离子载体的镉离子转运不受阻断。敏感菌株中能量依赖的镉离子摄取受到锰离子的抑制，动力学表明为竞争性抑制。有人提出，抗性菌株中镉离子的第二种低亲和力摄取系统是能量依赖的镉离子/质子反向转运体，在低镉离子浓度下其功能是净镉离子外流。
