Iron-related modification of bacterial transfer RNA

Abstract

Transfer RNAs isolated from E. coli grown in media where ferric iron is not freely available show well characterized chromatographic changes due to the absence of the methylthio moiety of ms²i⁶A. The altered tRNA molecules include tRNAtrp tRNA^tyr, tRNA^Phe and two minor tRNA^ser species. It has been suggested that methylthiolation of tRNA affects its function in regulation. We now show iron-related changes in tRNA^trp from S. typhimurium, Ps. aeruginosa and K. pneumouniae. tRNA^trP from S. typhimurium contains ms²i⁶A and it seems probable that the availability of iron affects the synthesis of ms²i⁶A-tRNA^trP from i⁶A-tRNA^trP in this organism. An iron-related methylthiolating system may also be operative in K. pneumoniae. S. marcescens tRNA^trp, however was not affected by the availability of iron. Neither ms²i⁶A nor i⁶A was found in S. marcescens tRNA, although an, as yet unidentified, hydrophobic nucleoside was present.