Cryo-EM reveals that Escherichia coli tRNA-transglycosylase can bind and act upon two tRNAs
Significance tRNA base-modification is an important mechanism for the regulation of protein expression on the RNA level. Several disease-causing bacteria use the enzyme tRNA-guanine transglycosylase (TGT) to upregulate translation of virulence factors which are essential for facilitating host infection. As such, TGT is a potential drug target for diseases like shigellosis. In this work, we present the cryo-EM structure of Escherichia coli TGT, identical to the Shigella enzyme, and investigate the structural basis of its interaction with tRNA. Our work reveals that, unlike all other known TGTs, the E. coli TGT homodimer forms covalent intermediates with two tRNAs. These findings advance our understanding of TGT enzymology and provide a structural foundation for the development of antibiotics and next-generation RNA-labeling tools.