N-Utilization Substance G (NusG) N-terminal domain in the NusG Specialized Paralog (SP), AnFA1
Regulation of the afp, antifeeding prophage, gene cluster is mediated by AnFA1, a RfaH-like transcriptional antiterminator. RfaH is an operon-specific virulence regulator, thought to arisen from an early duplication of N-Utilization Substance G (NusG). 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 antitermination factors. Orthologs of the NusG gene exist in all bacteria, but their functions and requirements are different. The NusG N-terminal domain (NGN) is similar in all NusG orthologs, but its C-terminal domain and the linker that separate these two domains are different. The domain organization of NusG and its orthologs suggests that the common properties of NusG and its orthologs and paralogs are due to their similar NGN domains.
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