Spanheimer R, Hoffmann M, Kögl S, Schmidt S, Pflüger K, Müller V
Molecular Microbiology and Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University Frankfurt, Frankfurt am Main, Germany.
J Mol Microbiol Biotechnol. 2008;15(4):255-63. doi: 10.1159/000108656. Epub 2007 Sep 20.
Methanogenic archaea accumulate glycine betaine in response to hypersalinity, but the regulation of proteins involved, their mechanism of activation and regulation of the corresponding genes are largely unknown. Methanosarcina mazei differs from most other methanoarchaea in having two gene clusters both encoding a potential glycine betaine transporter, Ota and Otb. Western blot as well as quantitative real-time PCR revealed that Otb is not regulated by osmolarity. On the other hand, cellular levels of Ota increased with increasing salt concentrations. A maximum was reached at 300-500 mM NaCl. Ota concentrations reached a maximum 4 h after an osmotic upshock. Hyperosmolarity also caused an increase in cellular Ota concentrations. In addition to osmolarity Ota expression was regulated by the growth phase. Expression of Ota as well as transport of betaine was downregulated in the presence of glycine betaine.
产甲烷古菌会因高盐度而积累甘氨酸甜菜碱，但参与其中的蛋白质的调控、它们的激活机制以及相应基因的调控在很大程度上尚不清楚。马氏甲烷八叠球菌与大多数其他甲烷古菌不同，它有两个基因簇，都编码一种潜在的甘氨酸甜菜碱转运蛋白，即Ota和Otb。蛋白质免疫印迹以及定量实时PCR显示，Otb不受渗透压调节。另一方面，Ota的细胞水平随着盐浓度的增加而升高。在300 - 500 mM NaCl时达到最大值。渗透压冲击后4小时，Ota浓度达到最大值。高渗也导致细胞中Ota浓度增加。除了渗透压，Ota的表达还受生长阶段的调控。在甘氨酸甜菜碱存在的情况下，Ota的表达以及甜菜碱的转运均被下调。
