The Candida albicans gene encoding the cytoplasmic leucyl-tRNA synthetase: implications for the evolution of CUG codon reassignment.
In a number of Candida species the 'universal' leucine codon CUG is decoded as serine. To help understand the evolution of such a codon reassignment we have analyzed the Candida albicans leucyl-tRNA synthetase (CaLeuRS) gene (CaCDC60). The predicted CaLeuRS sequence shows a significant level of amino acid identity to LeuRS from other organisms. A mitochondrial LeuRS (ScNAM2) homologue, which shared low identity with the CaLeuRS, was also identified in C. albicans. Antigenically-related LeuRSs were identified in a range of Candida species decoding the CUG codon as both serine and leucine, using an antibody raised against the N-terminal 15 amino acids of the CaLeuRS. Complementation experiments demonstrated that the CaLeuRS was able to functionally complement a Saccharomyces cerevisiae cdc60::kanMX null mutation. We conclude that there is no alteration in tRNA recognition and aminoacylation by the C. albicans LeuRS, which argues against it having a role in codon reassignment. The nucleotide sequences of the CaCDC60 and CaNAM2 genes were deposited at GenBank under Accession numbers AF293346 and AF352020, respectively.
O'Sullivan
J M
JM
Department of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, UK.
Mihr
M J
MJ
Santos
M A
MA
Tuite
M F
MF
D000595:Amino Acid Sequence; D002176:Candida albicans / Q000201:enzymology / Q000235:genetics*; D003001:Cloning, Molecular; D003062:Codon / Q000235:genetics; D003593:Cytoplasm / Q000201:enzymology; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics; D019143:Evolution, Molecular; D005800:Genes, Fungal / Q000235:genetics; D005815:Genetic Code / Q000235:genetics; D005816:Genetic Complementation Test; D007935:Leucine-tRNA Ligase / Q000235:genetics*; D008969:Molecular Sequence Data; D012441:Saccharomyces cerevisiae / Q000235:genetics; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
D003062:Codon; D004271:DNA, Fungal; D007935:Leucine-tRNA Ligase