Differential regulation of Ota and Otb, two primary glycine betaine transporters in the methanogenic archaeon Methanosarcina mazei go1

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 m M 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. Copyright (c) 2007 S. Karger AG, Basel.