title: Leishmania donovani Encodes a Functional Selenocysteinyl-tRNA Synthase.
abstract: The synthesis of selenocysteine, the 21st amino acid, occurs on its transfer RNA (tRNA), tRNA(Sec). tRNA(Sec) is initially aminoacylated with serine by seryl-tRNA synthetase and the resulting seryl moiety is converted to phosphoserine by O-phosphoseryl-tRNA kinase (PSTK) in eukaryotes. The selenium donor, selenophosphate is synthesized from selenide and ATP by selenophosphate synthetase. Selenocysteinyl-tRNA synthase (SepSecS) then uses the O-phosphoseryl-tRNA(Sec) and selenophosphate to form Sec-tRNA(Sec) in eukaryotes. Here, we report the characterization of selenocysteinyl-tRNA synthase from Leishmania donovani. Kinetoplastid SepSecS enzymes are phylogenetically closer to worm SepSecS. LdSepSecS was found to exist as a tetramer. Leishmania SepSecS enzyme was found to be active and able to complement the ΔselA deletion in Escherichia coli JS1 strain only in the presence of archaeal PSTK, indicating the conserved nature of the PSTK-SepSecS pathway. LdSepSecS was found to localize in the cytoplasm of the parasite. Gene deletion studies indicate that Leishmania SepSecS is dispensable for the parasite survival. The parasite was found to encode three selenoproteins, which were only expressed in the presence of SepSecS. Selenoproteins of L. donovani are not required for the growth of the promastigotes. Auranofin, a known inhibitor of selenoprotein synthesis showed the same sensitivity toward the wild-type and null mutants suggesting its effect is not through binding to selenoproteins. The three-dimensional structural comparison indicates that human and Leishmania homologs are structurally highly similar but their association modes leading to tetramerization seem different.
authors.affiliation: From the School of Life Sciences, Jawaharlal Nehru University, New Delhi, India.
authors.forename: Reetika
authors.initials: R
authors.lastname: Manhas
authors.affiliation: From the School of Life Sciences, Jawaharlal Nehru University, New Delhi, India.
authors.forename: Venkatraman Subramanian
authors.initials: VS
authors.lastname: Gowri
authors.affiliation: From the School of Life Sciences, Jawaharlal Nehru University, New Delhi, India rentala@outlook.com.
authors.forename: Rentala
authors.initials: R
authors.lastname: Madhubala
mesh_terms: D000595:Amino Acid Sequence; D000604:Amino Acyl-tRNA Synthetases / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001310:Auranofin / Q000494:pharmacology; D002460:Cell Line; D017124:Conserved Sequence; D003593:Cytoplasm / Q000201:enzymology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D017353:Gene Deletion; D007893:Leishmania donovani / Q000187:drug effects / Q000201:enzymology* / Q000254:growth & development / Q000472:pathogenicity; D008264:Macrophages / Q000469:parasitology; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D030781:Organisms, Genetically Modified; D010802:Phylogeny; D011487:Protein Conformation; D015800:Protozoan Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D051140:Selenoproteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D014774:Virulence
chemical_list: D004791:Enzyme Inhibitors; D015800:Protozoan Proteins; D012346:RNA, Transfer, Amino Acyl; D011994:Recombinant Proteins; D051140:Selenoproteins; C112705:selenocysteinyl-tRNA; D001310:Auranofin; D000604:Amino Acyl-tRNA Synthetases
keywords: Leishmania; aminoacyl tRNA synthetase; drug action; gene expression; selenoprotein