Diverse Mechanisms of Sulfur Decoration in Bacterial tRNA and Their Cellular Functions

Abstract

Sulfur-containing transfer ribonucleic acids (tRNAs) are ubiquitous biomolecules found in all organisms that possess a variety of functions. For decades, their roles in processes such as translation, structural stability, and cellular protection have been elucidated and appreciated. These thionucleosides are found in all types of bacteria; however, their biosynthetic pathways are distinct among different groups of bacteria. Considering that many of the thio-tRNA biosynthetic enzymes are absent in Gram-positive bacteria, recent studies have addressed how sulfur trafficking is regulated in these prokaryotic species. Interestingly, a novel proposal has been given for interplay among thionucleosides and the biosynthesis of other thiocofactors, through participation of shared-enzyme intermediates, the functions of which are impacted by the availability of substrate as well as metabolic demand of thiocofactors. This review describes the occurrence of thio-modifications in bacterial tRNA and current methods for detection of these modifications that have enabled studies on the biosynthesis and functions of S-containing tRNA across bacteria. It provides insight into potential modes of regulation and potential evolutionary events responsible for divergence in sulfur metabolism among prokaryotes.

Naturally occurring modified ribonucleosides

“…(h) Separately, in the production of mnm 5 se 2 U and cmnm 5 se 2 U, it has been speculated that formation of 5-aminomethyl-2-geranylthiouridine (nm 5 ges 2 U) and 5-aminomethyl-2-selenouridine (nm 5 se 2 U) can occur due to the possibility of decarboxylation of cmnm 5 ges 2 U and cmnm 5 se 2 U. The conversion from cmnm 5 ges 2 U and cmnm 5 se 2 U into nm 5 ges 2 U and nm 5 se 2 U is consistent with prior decarboxylation events with other precursors in this synthesis cascade (C. Zheng, Black, et al, 2017). (i) Historically, in vitro analysis of the effects of modifications on RNAs has been conducted through direct incorporation of the desired modification via synthetic means (reviewed in Dellafiore, Montserrat, & Iribarren, 2016;A.…”

The Response of Acinetobacter baumannii to Hydrogen Sulfide Reveals Two Independent Persulfide-Sensing Systems and a Connection to Biofilm Regulation

“…Included in this group of enzymes is MnmA, the tRNA 2-thiouridylase, which incorporates s 2 U substitution at U34 in tRNAs. The persulfidated Cys is the resolving Cys in a two-Cys mechanism that donates the sulfur atom for thio-insertion (53,54).…”

Bacterial wobble modifications of NNA‐decoding tRNAs

“…Isolation of tRNA harboring either the mnm 5 U or the s 2 U partially modified states indicates that the modifications are independent of each other (39,40). The original cmnm 5 U can also be further derivatized by either the IscS-MnmA or TrmL to yield cmnm 5 s 2 U or cmnm 5 Um, respectively (38,41,42).…”