Schizosaccharomyces pombe possesses two paralogous valyl-tRNA synthetase genes of mitochondrial origin.
Previous studies showed that VAS1 of Saccharomyces cerevisiae encodes both cytosolic and mitochondrial forms of valyl-tRNA synthetase (ValRS) through alternative initiation of translation. We show herein that except for Schizosaccharomyces pombe, all yeast species studied contained a single ValRS gene encoding both forms, and all of the mature protein forms deduced from those genes possessed an N-terminal appended domain (Ad) that was absent from their bacterial relatives. In contrast, S. pombe contained two distinct nuclear ValRS genes, one encoding the mitochondrial form and the other its cytosolic counterpart. Although the cytosolic form closely resembles other yeast ValRS sequences (approximately 60% identity), the mitochondrial form exhibits significant divergence from others (approximately 35% identity). Both genes are active and essential for the survival of the yeast. Most conspicuously, the mitochondrial form lacks the characteristic Ad. A phylogenetic analysis further suggested that both forms of S. pombe ValRS are of mitochondrial origin, and the mitochondrial form is ancestral to the cytoplasmic form.
Chiu
Wen-Chih
WC
Department of Life Science, National Central University, Jung-li, Taiwan.
Chang
Chia-Pei
CP
Wen
Wei-Ling
WL
Wang
Shao-Win
SW
Wang
Chien-Chia
CC
D000595:Amino Acid Sequence; D049148:Aminoacylation; D003593:Cytoplasm / Q000378:metabolism; D055786:Gene Knockout Techniques; D020043:Genes, Essential; D005800:Genes, Fungal; D005816:Genetic Complementation Test; D006651:Histocytochemistry; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D010802:Phylogeny; D017434:Protein Structure, Tertiary; D012568:Schizosaccharomyces / Q000166:cytology / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D014637:Valine-tRNA Ligase / Q000235:genetics* / Q000378:metabolism
D014637:Valine-tRNA Ligase