Abstract
Modifications of transfer RNA (tRNA) have been shown to play critical roles in the biogenesis, metabolism, structural stability and function of RNA molecules, and the specific modifications of nucleobases with sulfur atoms in tRNA are present in pro- and eukaryotes. Here, especially the thiomodifications xm5s2U at the wobble position 34 in tRNAs for Lys, Gln and Glu, were suggested to have an important role during the translation process by ensuring accurate deciphering of the genetic code and by stabilization of the tRNA structure. The trafficking and delivery of sulfur nucleosides is a complex process carried out by sulfur relay systems involving numerous proteins, which not only deliver sulfur to the specific tRNAs but also to other sulfur-containing molecules including iron–sulfur clusters, thiamin, biotin, lipoic acid and molybdopterin (MPT). Among the biosynthesis of these sulfur-containing molecules, the biosynthesis of the molybdenum cofactor (Moco) and the synthesis of thio-modified tRNAs in particular show a surprising link by sharing protein components for sulfur mobilization in pro- and eukaryotes.
Highlights
Sulfur is an essential element to all living organisms and the presence of sulfur in cofactors was discovered more than a century ago [1]
Rhodaneses are characterized by a 6-amino acid active-site loop with a conserved cysteine, and in vitro catalyze the transfer of a sulfane sulfur atom from thiosulfate to cyanide [3,6]. Both enzymes catalyze the formation of a persulfide group (R–S–SH) on specific conserved cysteine residues, which serves as a sulfur donor for the biosynthesis of numerous und diverse sulfur-containing biomolecules
The biosynthesis of molybdenum cofactor (Moco) can be divided into in the third step, the molybdenum atom is inserted into molybdopterin to form Moco; and (iv) additional2017, modification of Moco occurs in bacteria and archaea with the attachment of a nucleotide Biomolecules
Summary
Sulfur is an essential element to all living organisms and the presence of sulfur in cofactors was discovered more than a century ago [1]. The fact that the biosynthesis of Moco and the synthesis of thio-modified tRNAs share protein components essential for sulfur mobilization in pro- and eukaryotes for both pathways, reveals a surprising link regarding the biosynthesis of these sulfur-containing molecules. An additional thio-modification forming 5-taurinomethyl-2-thiouridine (τm s2 U34) has been identified, the synthesis of which requires different protein components This modification seem to be restricted to mammalian mitochondria only, since in other eukaryotes, including yeast, a cmnm s2 U34 tRNA modification is present in mitochondria [13] (Table 1). Protein of bacteria contrast, the In mcm modification the cytosol of more than different molybdoenzymes being involved in specific, usually non-essential eukaryotes involves the proteins molybdenum cofactor synthesis protein 3 (MOCS3), redox-reactions [28].
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