Disease relevance of SSK1

• Osmoregulation in Saccharomyces cerevisiae involves a multistep phosphorelay system requiring three proteins, SLN1, YPD1, and SSK1, that are related to bacterial two-component signaling proteins, in particular, those involved in regulating sporulation in Bacillus subtilis and anaerobic respiration in Escherichia coli [1].

High impact information on SSK1

• Pbs2p was activated by MAP kinase kinase kinases (MAPKKKs) Ssk2p and Ssk22p that are under the control of the SLN1-SSK1 two-component osmosensor [2].
• The SSK1 C-terminal receiver domain interacts with an N-terminal segment of SSK2 [3].
• The histidine-containing phosphotransfer (HPt) protein YPD1 is an osmoregulatory protein in yeast that facilitates phosphoryl transfer between the two response regulator domains associated with SLN1 and SSK1 [4].
• AhSSK1, despite having a similar secondary structure to other SKP1-like proteins, appeared quite distinctive in sequence and unique in a phylogenetic analysis, in which no SSK1 ortholog could be predicted in the sequenced genomes of Arabidopsis and rice [5].
• Defective hyphal development and avirulence caused by a deletion of the SSK1 response regulator gene in Candida albicans [6].

Biological context of SSK1

• Because the phosphorylation state largely determines the functional state of response regulator proteins, we have carried out a comparative study of the phosphorylated lifetimes of the three response regulator domains associated with SLN1, SSK1, and SKN7 (R1, R2, and R3, respectively) [7].
• The results confirmed our previous observation that CaSSK1, unlike SSK1 or mcs4(+), does not regulate cellular responses to either osmotic or oxidative stress [6].
• Finally, virulence studies indicated that SSK1 is essential for the pathogenesis of C. albicans, suggesting that the Ssk1p response regulator could be a good target for antifungal therapy [6].
• The homologous regulatory domains of SLN1 and SSK1 exhibit remarkably different phosphorylated half-lives, a finding that provides insight into the distinct roles that these phosphorylation-dependent regulatory domains play in the yeast osmosensory signal transduction pathway [1].

Anatomical context of SSK1

• Further, SSK1 appears to have a regulatory function in some aspects of cell wall biosynthesis [8].

Associations of SSK1 with chemical compounds

• We have previously shown that C. albicans SSK1 does not complement the ssk1 mutant of S. cerevisiae and that the ssk1 mutant of C. albicans is not sensitive to sorbitol [8].

Other interactions of SSK1

• Activation of the yeast SSK2 MAP kinase kinase kinase by the SSK1 two-component response regulator [3].

References