title: Inactivation of Saccharomyces cerevisiae sulfate transporter Sul2p: use it and lose it.
abstract: Saccharomyces cerevisiae SO(4)(=) transport is regulated over a wide dynamic range. Sulfur starvation causes ∼10,000-fold increase in the (35)SO(4)(=) influx mediated by transporters Sul1p and Sul2p; >80% of the influx is via Sul2p. Adding methionine to S-starved cells causes a 50-fold decline (t(1/2) ∼5 min) in SUL1 and SUL2 mRNA but a slower decline (t(1/2) ∼1 h) in transport. In contrast, SO(4)(=) addition does not affect mRNA but causes a rapid (t(1/2) = 2-4 min) decrease in transport. In met3Δ cells (unable to metabolize SO(4)(=)), addition of SO(4)(=) to S-starved cells causes inactivation of (35)SO(4)(=) influx over times in which cellular SO(4)(=) contents are nearly constant. The relationship between cellular SO(4)(=) and transport inactivation shows that cellular SO(4)(=) is not the signal for Sul2p inactivation. Instead, the transport inactivation rate has the same dependence on extracellular SO(4)(=) as (35)SO(4)(=) influx, indicating that Sul2p exhibits use-dependent inactivation; the transport process itself increases the probability of Sul2p inactivation and degradation. In addition, there is a transient efflux of SO(4)(=) shortly after adding >0.02 mM SO(4)(=) to S-starved met3Δ cells. This transient efflux provides further protection against excessive SO(4)(=) influx and may represent an alternate transport mode of Sul2p.
authors.affiliation: Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA. JenningsMichaelL@uams.edu
authors.forename: Michael L
authors.initials: ML
authors.lastname: Jennings
authors.forename: Jian
authors.initials: J
authors.lastname: Cui
mesh_terms: D027321:Anion Transport Proteins / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D025461:Feedback, Physiological; D007700:Kinetics; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D000076988:Sulfate Transporters; D013431:Sulfates / Q000378:metabolism*
chemical_list: D027321:Anion Transport Proteins; C094656:SUL1 protein, S cerevisiae; C105781:SUL2 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D000076988:Sulfate Transporters; D013431:Sulfates