The Conserved Cys-X ₁ -X ₂ -Cys Motif Present in the TtcA Protein Is Required for the Thiolation of Cytidine in Position 32 of tRNA from Salmonella enterica serovar Typhimurium

Abstract

The modified nucleoside 2-thiocytidine (s 2 C) has so far been found in tRNA from organisms belonging to the phylogenetic domains Archaea and Bacteria. In the bacteria Escherichia coli and Salmonella enterica serovar

The conserved Wobble uridine tRNA thiolase Ctu1–Ctu2 is required to maintain genome integrity

“…S3) and in a CXXC motif (C142A C145A; Fig. S3), both being expected to be required for the catalytic activity (6). In contrast to wild-type ctu1, neither the K62A D63A mutant nor the C142A C145A mutant could rescue the growth defect of the ctu1-deleted strain at 36°C or restore thiolation when introduced on a plasmid, although their expression levels were similar to that of the wild-type control (Fig.…”

“…Strikingly, the perfect alignment of the PP-loop of TtuA with Ctu1 orthologs extended to five conserved CXXC motifs required for the thiolase activity ( Fig. S3) (6).…”

“…TtcA, an enzyme responsible for the synthesis of 2-thiocytidine (S 2 C) ( Fig. S2) at position 32 of tRNA (6), is the closest Escherichia coli sequence to the Ctu1 protein family, but the S 2 C modification is not found in eukaryotic tRNAs. In contrast, the thiolation of the wobble uridine (S 2 U) at position 34 in tRNA LYS UUU , tRNA GLU UUC , and tRNA GLN UUG is conserved in nearly all species.…”

Redox Reactions of the Iron-Sulfur Cluster in a Ribosomal RNA Methyltransferase, RumA

“…The RumA cluster is ligated by 4 cysteines and the iron-binding sequence motif is CX 5 CX 2 CX n C. In contrast, the radical Sadenosyl-L-methionine enzymes, of which MiaB (7) and biotin synthase (8) are examples, have a [4Fe-4S] cluster built of a CX 3 CX 2 C sequence that leaves one iron of the cluster free to participate in catalysis. MiaB is a member of a family of enzymes catalyzing addition of sulfur to tRNA bases (9). The FeS sequence motifs in the DNA repair enzymes, endonuclease III (10) and MutY (11), are CX 6 CX 2 CX 5 C, somewhat similar to the RumA sequence.…”

Celebrating wobble decoding: Half a century and still much is new

“…99,100 Although the energy barrier for I○A base-pair formation is greater than those of I○C and I○U, the increased distance between the N-glycosyl bonds of I 34 and A3 required to accommodate the purine○purine wobble pair can be achieved when the nucleosides adopt an I anti ○A anti conformation. 1,44,101 Additional modifications at position 32 and 37 of the ASL Arg ICG may further contribute to the difficulties of I○A wobble pairing.…”