The Fps1p aquaglyceroporin facilitates the use of small aliphatic amides as a nitrogen source by amidase-expressing yeasts.

Saccharomyces cerevisiae acquires a resistance to high, toxic levels of acetic acid by destabilizing Fps1p, the plasma membrane aquaglyceroporin through which this acid - in its undissociated state - enters the cell. In this study, Fps1p loss was shown to confer resistances to acetic acid, acrolein and allyl alcohol, not just in S. cerevisiae but also in the osmotolerant spoilage yeast Zygosaccharomyces rouxii. However, in Z. rouxii, the loss of Fps1p severely compromised the use of acetamide and several other small amides as sources of nitrogen, an indication that these amides enter the cells of this yeast by passive diffusion through the Fps1p pore. Saccharomyces cerevisiae cannot grow on acetamide, but was conferred with an ability to use this and other small amides as nitrogen sources by heterologous expression of a Z. rouxii ORF (ZrAMD1) with protein sequence identity to the amdS-encoded amidase of Aspergillus nidulans. This capacity of ZrAMD1-expressing S. cerevisiae to assimilate amide nitrogen was severely compromised by the loss of Fps1p. ZrAMD1 appears to encode the major amidase of Z. rouxii as a Zramd1Delta deletant mutant had, like the Zrfps1Delta deletant, lost the ability to assimilate small amides as sources of nitrogen.