The genes encoding endonuclease VIII and endonuclease III in Escherichia coli are transcribed as the terminal genes in operons

Escherichia coli endonuclease VIII and endonuclease III are oxidative base excision repair DNA glycosylases that remove oxidized pyrimidines from DNA, The genes encoding these proteins, nei and nth, are both co-transcribed as the terminal genes in operons, nei is the terminal gene in an operon with four open reading frames that encode proteins of unknown function, This ope ron has two confirmed transcription initiation sites upstream of the first open reading frame and two transcript termination sites downstream of nei, nth is the terminal gene in an operon with seven open reading frames that e ncode proteins of unknown function. The six open reading frames immediately upstream of nth show homology to the genes rnfA, rnfB, rnfC, rnfD, rnfG an d rnfE from Rhodobacter capsulatis, The rnf genes are required for nitrogen fixation in R.capsulatis and have been predicted to make up a membrane com plex involved in electron transport to nitrogenase, The nth operon has tran scription initiation sites upstream of the first and second open reading fr ames and a single transcript termination site downstream of nth, The order of genes in these operons has been conserved or partially conserved in othe r bacteria, although it is not known whether the genes are co-transcribed i n these other organisms.