Delaney J M, Wall D, Georgopoulos C
Department of Cellular, Viral, and Molecular Biology, University of Utah School of Medicine, Salt Lake City 84132.
J Bacteriol. 1993 Jan;175(1):166-75. doi: 10.1128/jb.175.1.166-175.1993.
The Escherichia coli htrD gene was originally isolated during a search for new genes required for growth at high temperature. Insertional inactivation of htrD leads to a pleiotropic phenotype characterized by temperature-sensitive growth in rich medium, H2O2 sensitivity, and sensitivity to cysteine. The htrD gene was cloned and sequenced, and an htrD::mini-Tn10 insertion mutation was mapped within this gene. The htrD gene was shown to encode a protein of approximately 17.5 kDa. Expression of the htrD gene was examined by using an phi (htrD-lacZ) operon fusion. It was found that htrD is not temperature regulated and therefore is not a heat shock gene. Further study revealed that htrD expression is increased under aerobic growth conditions. Conversely, under anaerobic growth conditions, htrD expression is decreased. In addition, a mutation within the nearby cydD gene was found to drastically reduce htrD expression under all conditions tested. These results indicate that htrD is somehow involved in aerobic respiration and that the cydD gene product is necessary for htrD gene expression. In agreement with this conclusion, htrD mutant bacteria are unable to oxidize the cytochrome d-specific electron donor N,N,N',N'-tetramethyl-p-phenylenediamine.
大肠杆菌htrD基因最初是在寻找高温生长所需新基因的过程中分离得到的。htrD的插入失活导致多效性表型，其特征为在丰富培养基中温度敏感生长、对过氧化氢敏感以及对半胱氨酸敏感。htrD基因被克隆并测序，一个htrD::mini-Tn10插入突变被定位在该基因内。htrD基因被证明编码一种约17.5 kDa的蛋白质。通过使用一个φ(htrD - lacZ)操纵子融合体来检测htrD基因的表达。发现htrD不受温度调节，因此不是一个热休克基因。进一步研究表明，htrD的表达在有氧生长条件下增加。相反，在厌氧生长条件下，htrD的表达降低。此外，发现在附近的cydD基因内的一个突变在所有测试条件下都能大幅降低htrD的表达。这些结果表明htrD以某种方式参与有氧呼吸，并且cydD基因产物对于htrD基因表达是必需的。与这一结论一致的是，htrD突变细菌无法氧化细胞色素d特异性电子供体N,N,N',N'-四甲基对苯二胺。
