Tahara Hiroko, Uchiyama Junji, Yoshihara Toshihiro, Matsumoto Kouji, Ohta Hisataka
Department of Biology, Tokyo University of Science, Shinjuku, Tokyo, Japan.
Biochim Biophys Acta. 2012 Aug;1817(8):1360-6. doi: 10.1016/j.bbabio.2012.02.035. Epub 2012 Mar 5.
ATP-binding cassette (ABC) transporter proteins mediate energy-dependent transport of substrates across cell membranes. Numerous ABC transporter-related genes have been found in the Synechocystis sp. PCC6803 genome by genome sequence analysis including H(+), iron, phosphate, polysaccharide, and CO(2) transport-related genes. The substrates of many other ABC transporters are still unknown. To identify ABC transporters involved in acid tolerance, deletion mutants of ABC transporter genes with unknown substrates were screened for acid stress sensitivities in low pH medium. It was found that cells expressing the deletion mutant of slr1045 were more sensitive to acid stress than the wild-type cells. Moreover, slr1045 expression in the wild-type cells was increased under acid stress. These results indicate that slr1045 is an essential gene for survival under acid stress. The mutant displayed high osmotic stress resistance and high/low temperature stress sensitivity. Considering the temperature-sensitive phenotype and homology to the organic solvent-resistant ABC system, we subsequently compared the lipid profiles of slr1045 mutant and wild-type cells by thin-layer chromatography. In acid stress conditions, the phosphatidylglycerol (PG) content in the slr1045 mutant cells was approximately 40% of that in the wild-type cells. Moreover, the addition of PG to the medium compensated for the growth deficiency of the slr1045 mutant cells under acid stress conditions. These data suggest that slr1045 plays a role in the stabilization of cell membranes in challenging environmental conditions. This article is part of a Special Issue entitled: Photosynthesis Research for Sustainability: from Natural to Artificial.
ATP结合盒（ABC）转运蛋白介导底物跨细胞膜的能量依赖性转运。通过基因组序列分析，在集胞藻PCC6803基因组中发现了许多与ABC转运蛋白相关的基因，包括与氢离子、铁、磷酸盐、多糖和二氧化碳转运相关的基因。许多其他ABC转运蛋白的底物仍然未知。为了鉴定参与耐酸性的ABC转运蛋白，我们在低pH培养基中筛选了底物未知的ABC转运蛋白基因缺失突变体的酸胁迫敏感性。结果发现，表达slr1045缺失突变体的细胞比野生型细胞对酸胁迫更敏感。此外，野生型细胞中slr1045的表达在酸胁迫下增加。这些结果表明，slr1045是酸胁迫下生存所必需的基因。该突变体表现出高渗透压抗性和高/低温胁迫敏感性。考虑到其温度敏感表型和与有机溶剂抗性ABC系统的同源性，我们随后通过薄层色谱比较了slr1045突变体和野生型细胞的脂质谱。在酸胁迫条件下，slr1045突变体细胞中的磷脂酰甘油（PG）含量约为野生型细胞的40%。此外，在培养基中添加PG可补偿酸胁迫条件下slr1045突变体细胞的生长缺陷。这些数据表明，slr1045在挑战性环境条件下的细胞膜稳定中发挥作用。本文是名为：可持续性光合作用研究：从自然到人工的特刊的一部分。
