9.B.131.1.9
Cwh43 protein of 971 aas and 19 or 24 aas in a (1 + 2 + 3)^{3 or 4} TMS arrangement.
The last 5 peaks of hydrophobicity are small, and may or may not be TMSs. This protein plays a role in genetically controlled mechanisms of cell division and quiescence as cells respond to changes in the nutritional environment and for cell survival (Nakazawa et al. 2019). Temperature-sensitive (ts) mutants of the cwh43 gene in fission yeast abolish both cell proliferation and nitrogen starvation-induced G0 quiescence. Cwh43 encodes an evolutionarily conserve protein that localizes to the endoplasmic reticulum (ER). Defects in it fail to divide in low glucose, lose mitotic competence under nitrogen starvation, and affect lipid metabolism. Mutations of the pmr1 gene, which encodes an evolutionarily conserved Ca²⁺/Mn²⁺-transporting P-type ATPase, are potent extragenic suppressors of ts mutants of the cwh43 gene. These pmr1 mutations suppressed the ts phenotype of cwh43 mutants, among five P-type Ca²⁺- and/or Mn²⁺-ATPases reported in this organism. Cwh43 and Pmr1 co-localize to the ER. In cwh43 mutant cells, addition of excessive manganese to culture media enhances the severe defect in cell morphology and causes abnormal accumulation of a cell wall component, 1, 3-beta-glucan. In contrast, these abnormal phenotypes are abolished by deletion of the pmr1⁺ gene, as well as by removal of Mn²⁺ from the culture medium. Nutrition-related phenotypes of cwh43 mutant cells were rescued in the absence of Pmr1. These observations indicate that the cellular processes regulated by Cwh43 are appropriately balanced with Pmr1-mediated Mn²⁺ transport into the ER (Nakazawa et al. 2019).