Biosynthesis of Threonylcarbamoyl Adenosine (t6A), a Universal tRNA Nucleoside

NMR-based Structural Analysis of Threonylcarbamoyl-AMP Synthase and Its Substrate Interactions

“…TsaC has been shown to interact with three small substrates, L-threonine (25), ATP (24), and CO 2 /HCO 3 Ϫ (17), as well as hypomodified tRNA (24,25,27), TsaD and TsaB (16). The synthesis of TC-AMP, the central role of TsaC in t 6 A 37 biosynthesis, requires a number of intermolecular interactions and enzymatic activity.…”

“…Protein Expression and Purification-Protein samples were expressed and purified as described previously (16). For iso- (33).…”

“…This is supported by the increase in translational frameshifts in cells lacking the ability to form t 6 A 37 (13)(14)(15). Recent studies of the t 6 A 37 biosynthesis pathway have identified the following four proteins in Escherichia coli that are necessary and sufficient for in vitro formation of the modification: TsaC, TsaD, TsaE, and TsaB, also known as YrdC, YgjD, YjeE, and YeaZ, respectively (16). Two of the four proteins essential to the enzyme complex are unique to bacteria, TsaB and TsaE.…”

“…TsaC is essential in E. coli, but Sua5 is not essential in S. cerevisiae (24), even though both appear to have similar roles in t 6 A 37 biosynthesis. E. coli TsaC selectively binds both ATP and L-threonine (24,25) and is the sole protein of the t 6 A-synthase complex capable of L-threonine-dependent conversion of ATP to AMP (16). More recently, both TsaC and its B. subtilis homolog, YwlC, have been shown to catalyze the formation of the activated precursor L-threonylcarbamoyl-AMP (TC-AMP) from L-threonine, ATP, and CO 2 /HCO 3 Ϫ (Fig.…”

Kinase-associated Endopeptidase 1 (Kae1) Participates in an Atypical Ribosome-associated Complex in the Apicoplast of Plasmodium falciparum

“…In eukaryotes and Archaea, this functional unit is called endopeptidase, kinase, chromatin-associated (EKC; Kae1 was formerly thought to be an endopeptidase) (4) or kinase, endopeptidase, and other proteins of small size (KEOPS) (5) and comprises Kae1, the dimerization module Pcc1, the kinase/ATPase Bud32, and Cgi121, which is thought to allosterically regulate Bud32. The DEZ complex (YgjD-YjeEYeaZ) is the prokaryotic counterpart to the EKC/KEOPS com-plex, and it is made up of Kae1, YrdC, and two proteins of unknown function called YeaZ and YjeE (9,14). Interestingly, it was recently reported in yeast that the mitochondrial Kae1 homologue Qri7 can modify tRNA in the absence of protein binding partners (13).…”