Functional analysis of the Ashbya gossypii Fps1 homolog

Poster (konferens), 2010

Saccharomyces cerevisiae aquaglyceroporin Fps1 plays a central role in yeast osmoregulation, controlling the intracellular level of the compatible solute glycerol. When a cell encounter hyperosmotic conditions, Fps1 closes rapidly to ensure retention and accumulation of glycerol. In adaptation to lower external osmolarity, Fps1 opens again to release glycerol and hence turgor pressure. Mutants lacking Fps1 can not withstand a hypo-osmotic shock as well as wild type cells. Fps1 has unusually long N- and C-terminal extensions, and regulatory domains that are crucial for the gating mechanism have been identified on both termini. Fps1 also facilitates passive uptake of other small molecules such as arsenite and acidic acid. The filamentous fungi Ashbya gossypii Fps1 homolog (AgFps1) has shorter termini than Fps1. The aim of this study is to determine the function of AgFps1 by heterologous expression in S. cerevisiae fps1Δ mutants, and to study the physiological role of AgFps1 by deletion analysis in Ashbya gossypii. We can show that heterologous expression of AgFps1 in S. cerevisiae can substitute for Fps1 by releasing excessive glycerol upon a hypo-osmotic shock. AgFps1 expressed in S. cerevisiae appears to be hyperactive under hyperosmotic conditions, and exchanging the N- and C-terminal extensions for the corresponding termini of Fps1 is not sufficient to generate a regulated channel. Further, successful deletion of AgFPS1 renders an Ashbya gossypii mutant more resistant to arsenite than wild type fungi, indicating that AgFps1 transports arsenite.