Analysis of the pore of the unusual major intrinsic protein channel, yeast Fps1p

Fps1p is a glycerol efflux channel from Saccharomyces cerevisiae. In this atypical major intrinsic protein neither of the signature NPA motifs of the family, which are part of the pore, is preserved. To understand the functional consequences of this feature, we analyzed the pseudo-NPA motifs of Fps1p by site-directed mutagenesis and assayed the resultant mutant proteins in vivo. In addition, we took advantage of the fact that the closest bacterial homolog of Fps1p, Escherichia coli GlpF, can be functionally expressed in yeast, thus enabling the analysis in yeast cells of mutations that make this typical major intrinsic protein more similar to Fps1p. We observed that mutations made in Fps1p to "restore" the signature NPA motifs did not substantially affect channel function. In contrast, when GlpF was mutated to resemble Fps1p, all mutants had reduced activity compared with wild type. We rationalized these data by constructing models of one GlpF mutant and of the transmembrane core of Fps1p. Our model predicts that the pore of Fps1p is more flexible than that of GlpF. We discuss the fact that this may accommodate the divergent NPA motifs of Fps1p and that the different pore structures of Fps1p and GlpF may reflect the physiological roles of the two glycerol facilitators

The impact of climate change and variability on the generation of electrical power

Climate variability and change affect electricity generation in several ways. Electricity generation is directly dependent on climate/weather parameters like wind (wind power generation) or air temperature and resulting water temperature (thermal power plants). River discharge as a result of precipitation and temperature, the latter being one main factor influencing evapotranspiration, is important for hydro power generation and cooling of thermal power plants. In this study possible effects of climate variability and change on electricity generation in Germany are analyzed. Considered is electricity generation by thermal power plants, wind power plants and hydro power plants. While hydro power plants and thermal power plants are affected negatively due to declining river discharge or higher water temperatures, for wind power generation no clear tendency was found. The reduction for hydro power generation could be leveled out by a slight increase in installed capacity and modernization of turbines and generators. By a replacement of old once-through cooling systems by closed-circuit cooling systems for new thermal power plants the negative impacts on electricity generation can be reduced significantly. The planned increase of installed capacity for wind power generation clearly surpasses the changes arising from climate change