Trombe M C, Lanéelle G, Sicard A M
J Bacteriol. 1984 Jun;158(3):1109-14. doi: 10.1128/jb.158.3.1109-1114.1984.
It is possible to select transmembrane potential (delta psi)-altered mutants in Streptococcus pneumoniae on the basis of their resistance to the antifolate methotrexate. Comparison of such a mutant strain ( amiA9 ) with its parent was used to evaluate the role of delta psi in the uptake of certain amino acids. The delta psi-dependent uptake of isoleucine, leucine, valine, and asparagine showed a reduced maximum velocity of uptake, and decrease in the transport constant of the energy-dependent, delta psi-independent uptake of lysine, methionine, and glutamine was observed. No reduction of the intracellular pool of ATP or of lactate excretion could be detected in the mutant strain. Moreover, studies on membrane preparations suggest that the phenotype expressed by the amiA mutation is not a consequence of alteration of its ATPase activity or susceptibility to N,N'-dicyclohexylcarbodiimide. Therefore, it is unlikely that the amiA mutation affects the H+ F1F0 ATPase which is involved in the establishment of the proton motive force in anaerobic bacteria. We propose that another function contributes to delta psi in S. pneumoniae. The amiA gene may be the structural gene of that function.
基于肺炎链球菌对抗叶酸剂甲氨蝶呤的抗性，可以筛选出跨膜电位（δψ）改变的突变体。将这样一个突变菌株（amiA9）与其亲本进行比较，以评估δψ在某些氨基酸摄取中的作用。异亮氨酸、亮氨酸、缬氨酸和天冬酰胺的δψ依赖性摄取显示摄取的最大速度降低，并且观察到赖氨酸、蛋氨酸和谷氨酰胺的能量依赖性、δψ非依赖性摄取的转运常数下降。在突变菌株中未检测到细胞内ATP池或乳酸排泄的减少。此外，对膜制剂的研究表明，amiA突变所表达的表型不是其ATP酶活性改变或对N，N'-二环己基碳二亚胺敏感性改变的结果。因此，amiA突变不太可能影响参与厌氧细菌质子动力势建立的H+ F1F0 ATP酶。我们提出另一种功能对肺炎链球菌中的δψ有贡献。amiA基因可能是该功能的结构基因。
