A functional Rim101 complex is required for proper accumulation of the Ena1 Na+-ATPase protein in response to salt stress in Saccharomyces cerevisiae.

The maintenance of ionic homeostasis is essential for cell viability, thus the activity of plasma membrane ion transporters must be tightly controlled. Previous studies in Saccharomyces cerevisiae revealed that the proper trafficking of several nutrient permeases requires the E3 ubiquitin ligase Rsp5 and, in many cases, the presence of specific adaptor proteins needed for Rsp5 substrate recognition. Among these adaptor proteins are nine members of the arrestin-related trafficking adaptor (ART) family.

Genetic alterations leading to increases in internal potassium concentrations are detrimental for DNA integrity in Saccharomyces cerevisiae.

We have investigated the effects of alterations in potassium homeostasis on cell cycle progression and genome stability in Saccharomyces cerevisiae. Yeast strains lacking the PPZ1 and PPZ2 phosphatase genes, which aberrantly accumulate potassium, are sensitive to agents causing replicative stress or DNA damage and present a cell cycle delay in the G(1) /S phase. A synthetic slow growth phenotype was identified in a subset of DNA repair mutants upon inhibition of Ppz activity.

A complex of catalytically inactive protein phosphatase-1 sandwiched between Sds22 and inhibitor-3.

Protein Ser/Thr phosphatase-1 (PP1) associates with a host of proteins to form substrate-specific holoenzymes. Sds22 and Inhibitor-3 (I3) are two independently described ancient interactors of PP1. We show here by various approaches that Sds22 and I3 form a heterotrimeric complex with PP1, both in cell lysates and after purification.

YPI1 and SDS22 proteins regulate the nuclear localization and function of yeast type 1 phosphatase Glc7.

We have recently characterized Ypi1 as an inhibitory subunit of yeast Glc7 PP1 protein phosphatase. In this work we demonstrate that Ypi1 forms a complex with Glc7 and Sds22, another Glc7 regulatory subunit that targets the phosphatase to substrates involved in cell cycle control. Interestingly, the combination of equimolar amounts of Ypi1 and Sds22 leads to an almost full inhibition of Glc7 activity.

Structure-function analysis of the alpha5 and the alpha13 helices of human glucokinase: description of two novel activating mutations.

It was recently described that the alpha5 and the alpha13 helices of human pancreatic glucokinase play a major role in the allosteric regulation of the enzyme. In order to understand the structural importance of these helices, we have performed site-directed mutagenesis to generate glucokinase derivatives with altered residues. We have analyzed the kinetic parameters of these mutated forms and compared them with wild-type and previously defined activating mutations in these helices (A456V and Y214C).