A glycolytic enzyme, enolase, is recruited as a cofactor of tRNA targeting toward mitochondria in Saccharomyces cerevisiae.
In many organisms, mitochondria import nuclear DNA-encoded small RNAs. In yeast Saccharomyces cerevisiae, one out of two cytoplasmic isoacceptor tRNAs(Lys) is partially addressed into the organelle. Mitochondrial targeting of this tRNA was shown to depend on interaction with the precursor of mitochondrial lysyl-tRNA synthetase, preMsk1p. However, preMsk1p alone was unable to direct tRNA targeting, suggesting the existence of additional protein factor(s). Here, we identify the glycolytic enzyme, enolase, as such a factor. We demonstrate that recombinant enolase and preMSK1p are sufficient to direct tRNA import in vitro and that depletion of enolase inhibits tRNA import in vivo. Enzymatic and tRNA targeting functions of enolase appear to be independent. Three newly characterized properties of the enolase can be related to its novel function: (1) specific affinity to the imported tRNA, (2) the ability to facilitate formation of the complex between preMsk1p and the imported tRNA, and (3) partial targeting toward the mitochondrial outer membrane. We propose a model suggesting that the cell exploits mitochondrial targeting of the enolase in order to address the tRNA toward peri-mitochondrially synthesized preMsk1p. Our results indicate an alternative molecular chaperone function of glycolytic enzyme enolase in tRNA mitochondrial targeting.
Entelis
Nina
N
Department of "Molecular and Cellular Genetics," UMR 7156, CNRS-Université Louis Pasteur, Strasbourg 67084, France.
Brandina
Irina
I
Kamenski
Piotr
P
Krasheninnikov
Igor A
IA
Martin
Robert P
RP
Tarassov
Ivan
I
D027682:Cation Transport Proteins / Q000378:metabolism; D002451:Cell Compartmentation; D008928:Mitochondria / Q000201:enzymology* / Q000235:genetics* / Q000378:metabolism; D008954:Models, Biological; D010751:Phosphopyruvate Hydratase / Q000378:metabolism*; D011485:Protein Binding; D021381:Protein Transport; D034443:RNA Transport; D012343:RNA, Transfer / Q000378:metabolism*; D038744:Ribosomal Protein S6 Kinases, 90-kDa / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D012995:Solubility
D027682:Cation Transport Proteins; D029701:Saccharomyces cerevisiae Proteins; C068664:TRK1 protein, S cerevisiae; D012343:RNA, Transfer; D038744:Ribosomal Protein S6 Kinases, 90-kDa; C116919:mitogen and stress-activated protein kinase 1; D010751:Phosphopyruvate Hydratase