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N-Utilization Substance G (NusG) N-terminal domain in the NusG Specialized Paralog (SP), TaA The N-Utilization Substance G (NusG) protein is involved in transcription elongation and termination. NusG is essential in Escherichia coli and is associated with RNA polymerase elongation and Rho-termination in bacteria. Paralogs of eubacterial NusG, NusG SP (Specialized Paralog of NusG), are more diverse and often found as the first ORF in operons encoding secreted proteins and LPS biosynthesis genes. NusG SP family members are operon-specific transcriptional antiterminationn factors. TaA is a NusG SP factor that is required for synthesis of a polyketide antibiotic TA in Myxococcus xanthus. Orthologs of the NusG gene exist in all bacteria, but its functions and requirements are different. The NusG N-terminal (NGN) domain is quite similar in all NusG orthologs, but its C-terminal domains and the linker that separate these two domains are different. The domain organization of NusG and its orthologs suggest that the common properties of NusG and its orthologs and paralogs are due to their similar NGN domains.
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