title: Mdm31 protein mediates sensitivity to potassium ionophores but does not regulate mitochondrial morphology or phospholipid trafficking in Schizosaccharomyces pombe.
abstract: Mdm31p is an inner mitochondrial membrane (IMM) protein with unknown function in Saccharomyces cerevisiae. Mutants lacking Mdm31p contain only a few giant spherical mitochondria with disorganized internal structure, altered phospholipid composition and disturbed ion homeostasis, accompanied by increased resistance to the electroneutral K+ /H+ ionophore nigericin. These phenotypes are interpreted as resulting from diverse roles of Mdm31p, presumably in linking mitochondrial DNA (mtDNA) to the machinery involved in segregation of mitochondria, in mediating cation transport across IMM and in phospholipid shuttling between mitochondrial membranes. To investigate which of the roles of Mdm31p are conserved in ascomycetous yeasts, we analysed the Mdm31p orthologue in Schizosaccharomyces pombe. Our results demonstrate that, similarly to its S. cerevisiae counterpart, SpMdm31 is a mitochondrial protein and its absence results in increased resistance to nigericin. However, in contrast to S. cerevisiae, Sz. pombe cells lacking SpMdm31 are also less sensitive to the electrogenic K+ ionophore valinomycin. Moreover, mitochondria of the fission yeast mdm31Δ mutant display no changes in morphology or phospholipid composition. Therefore, in terms of function, the two orthologous proteins appear to have considerably diverged between these two evolutionarily distant yeast species, possibly sharing only their participation in ion homeostasis.
authors.affiliation: Departments of Biochemistry and Genetics, Comenius University, Faculty of Natural Sciences, Bratislava, Slovakia.
authors.forename: Branislav
authors.initials: B
authors.lastname: Ivan
authors.forename: Dana
authors.initials: D
authors.lastname: Lajdova
authors.forename: Lenka
authors.initials: L
authors.lastname: Abelovska
authors.forename: Maria
authors.initials: M
authors.lastname: Balazova
authors.forename: Jozef
authors.initials: J
authors.lastname: Nosek
authors.forename: Lubomir
authors.initials: L
authors.lastname: Tomaska
mesh_terms: D001692:Biological Transport; D008928:Mitochondria / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D010743:Phospholipids / Q000378:metabolism*; D061216:Potassium Ionophores / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D012568:Schizosaccharomyces / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C497847:Mdm31 protein, S cerevisiae; C000602289:Mdm31 protein, S pombe; D024101:Mitochondrial Proteins; D010743:Phospholipids; D061216:Potassium Ionophores; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins