Identification and evolution of fungal mitochondrial tyrosyl-tRNA synthetases with group I intron splicing activity.
The bifunctional Neurospora crassa mitochondrial tyrosyl-tRNA synthetase (CYT-18 protein) both aminoacylates mitochondrial tRNA(Tyr) and acts as a structure-stabilizing splicing cofactor for group I introns. Previous studies showed that CYT-18 has distinct tRNA(Tyr) and group I intron-binding sites, with the latter formed by three small "insertions" in the nucleotide-binding fold and other structural adaptations compared with nonsplicing bacterial tyrosyl-tRNA synthetases. Here, analysis of genomic sequences shows that mitochondrial tyrosyl-tRNA synthetases with structural adaptations similar to CYT-18's are uniquely characteristic of fungi belonging to the subphylum Pezizomycotina, and biochemical assays confirm group I intron splicing activity for the enzymes from several of these organisms, including Aspergillus nidulans and the human pathogens Coccidioides posadasii and Histoplasma capsulatum. By combining multiple sequence alignments with a previously determined cocrystal structure of a CYT-18/group I intron RNA complex, we identify conserved features of the Pezizomycotina enzymes related to group I intron and tRNA interactions. Our results suggest that mitochondrial tyrosyl-tRNA synthetases with group I intron splicing activity evolved during or after the divergence of the fungal subphyla Pezizomycotina and Saccharomycotina by a mechanism involving the concerted differentiation of preexisting protein loop regions. The unique group I intron splicing activity of these fungal enzymes may provide a new target for antifungal drugs.
Paukstelis
Paul J
PJ
Institute for Cellular and Molecular Biology, Department of Chemistry and Biochemistry, and Section of Molecular Genetics and Microbiology, School of Biological Sciences, University of Texas, Austin, TX 78712, USA.
Lambowitz
Alan M
AM
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000935:Antifungal Agents / Q000737:chemistry / Q000494:pharmacology; D001233:Aspergillus nidulans / Q000201:enzymology / Q000235:genetics; D003045:Coccidioides / Q000201:enzymology / Q000235:genetics; D017124:Conserved Sequence; D019143:Evolution, Molecular; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006658:Histoplasma / Q000201:enzymology / Q000235:genetics; D007438:Introns / Q000235:genetics*; D008928:Mitochondria / Q000201:enzymology; D024101:Mitochondrial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009492:Neurospora crassa / Q000201:enzymology / Q000235:genetics; D011487:Protein Conformation; D012331:RNA, Fungal / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D020539:Sequence Analysis, Protein; D014443:Tyrosine / Q000378:metabolism; D014448:Tyrosine-tRNA Ligase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D000935:Antifungal Agents; D005656:Fungal Proteins; D024101:Mitochondrial Proteins; D012331:RNA, Fungal; D014443:Tyrosine; D014448:Tyrosine-tRNA Ligase