Fig. 4.

Phosphotransfer assays for Gln-404 substitution mutants. Phospho-MBP-NarX was isolated and mixed with NarL. Proteins were resolved by Laemmli gel electrophoresis, and phosphorylation was measured by phosphorimaging as described in Materials and Methods. ●, phospho-NarL; (A) ○, phospho-MBP-NarX wild type; (B) ◇, phospho-MBP-NarX Q404H; (C) △, phospho-MBP-NarX Q404A; (D) ▽, phospho-MBP-NarX Q404E; (E) □, phospho-MBP-NarX Q404H. Data are representative of at least two independent experiments for each mutant.