<p> NusA, or N utilisation substance protein A, is a bacterial transcription termination factor. It binds to RNA polymerase alpha subunit and promotes termination at certain RNA hairpin structures. It is named for the interaction in <taxon tax_id="562">Escherichia coli</taxon> of <taxon tax_id="10710">Bacteriophage lambda</taxon> antitermination protein N with the N-utilisation substance, consisting of NusA, NusB, NusE (ribosomal protein S10), and NusG [<cite idref="PUB00013514"/>]. This entry represents an acidic 50-residue region found in two copies toward the C terminus of most proteobacterial NusA proteins, spaced about 26 residues apart. Analogous C-terminal extensions in some other bacterial lineages lack apparent homology but appear similarly acidic </p>