Tim54p connects inner membrane assembly and proteolytic pathways in the mitochondrion.
Tim54p, a component of the inner membrane TIM22 complex, does not directly mediate the import of inner membrane substrates but is required for assembly/stability of the 300-kD TIM22 complex. In addition, Deltatim54 yeast exhibit a petite-negative phenotype (also observed in yeast harboring mutations in the F1Fo ATPase, the ADP/ATP carrier, mitochondrial morphology components, or the i-AAA protease, Yme1p). Interestingly, other import mutants in our strain background are not petite-negative. We report that Tim54p is not involved in maintenance of mitochondrial DNA or mitochondrial morphology. Rather, Tim54p mediates assembly of an active Yme1p complex, after Yme1p is imported via the TIM23 pathway. Defective Yme1p assembly is likely the major contributing factor for the petite-negativity in strains lacking functional Tim54p. Thus, Tim54p has two independent functions: scaffolding/stability for the TIM22 membrane complex and assembly of Yme1p into a proteolytically active complex. As such, Tim54p links protein import, assembly, and turnover pathways in the mitochondrion.
Hwang
David K
DK
Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095, USA.
Claypool
Steven M
SM
Leuenberger
Danielle
D
Tienson
Heather L
HL
Koehler
Carla M
CM
D049069:ATP-Dependent Proteases; D000251:Adenosine Triphosphatases / Q000378:metabolism; D004272:DNA, Mitochondrial / Q000378:metabolism; D015870:Gene Expression; D005947:Glucose / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000378:metabolism; D050296:Microbial Viability; D008928:Mitochondria / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins / Q000172:deficiency / Q000378:metabolism*; D051336:Mitochondrial Membranes / Q000378:metabolism*; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*
D004272:DNA, Mitochondrial; D026901:Membrane Transport Proteins; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D029701:Saccharomyces cerevisiae Proteins; C102549:TIM22 protein, S cerevisiae; C110036:TIM54 protein, S cerevisiae; D049069:ATP-Dependent Proteases; C082702:YME1 protein, S cerevisiae; D000251:Adenosine Triphosphatases; D005947:Glucose