Conservation of amino acid sequences of NAGS from 25 organisms. The sizes of letters indicate the degree of conservation. Residues that are important for arginine binding are highlighted in yellow. Invariant residues are shown in blue. Asterisks indicate invariant residues that are mutated in arginine-insensitive NAGS from E. coli. Arrows indicate conserved amino acids that are absent or replaced by other amino acids in E. coli NAGK, which is not inhibited by arginine. Amino acids that were mutated in this study are shown in red; mutations in the mouse NAGS are shown in green; mutations in the X. campestris NAGS-K are in purple. LOGO-alignment was generated using NAGS sequences from five mammals (human, mouse, rat, dog and cow), two amphibians (X. laevis and X. tropicalis), zebrafish, pufferfish, freshwater pufferfish, arabidopsis, soy, tomato, rice, corn and 11 bacteria (E. coli, R. eutropha, N. gonorrhoeae, P aeruginosa, P. syringiae, X. campestris, X. axonopodis, X. fastidiosa, P. bermudensis, O. alexandrii and M. maris), which were aligned using ClustalW.