ISSN:
1432-0983
Keywords:
Key words Fission yeast
;
Nitrogen catabolite inactivation
;
pub1 ubiquitin ligase
;
spc1 stress-activated MAPK
;
Leucine transport
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Fission yeast strains auxotrophic for leucine are unable to proliferate in normally supplemented minimal media adjusted to pH 6.4 or above. High-pH sensitivity can be suppressed by the loss of Pub1, an E3 ubiquitin ligase, or by the replacement of NH4 + with a non-repressing source of nitrogen such as L-proline. In this report we show pub1 to be required for the rapid down-regulation of leucine uptake observed in response to the addition of NH4 + to the growth media. Furthermore, we corroborate earlier results demonstrating the transport of leucine to be negatively influenced by high extracellular pH. pub1 is homologous to the budding yeast nitrogen permease inactivator, NPI1/RSP5, which mediates the ubiquitination and subsequent destruction of NH4 +-sensitive permeases. The high-pH sensitivity of cells auxotrophic for leucine thus seems to reflect an inability of NH4 +-insensitive permeases to transport sufficient leucine under conditions where the proton gradient driving nutrient transport is low, and NH4 +-sensitive permeases have been destroyed. Intriguingly, the partial suppression of both high pH sensitivity, and the inactivating effect of NH4 + on leucine transport, seen in pub1-1 point mutants, becomes as complete as seen in pub1Δ backgrounds when cells have concomitantly lost the function of the spc1 stress-activated MAPK.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s002940050457
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