Fig. 4. The C-terminal domain of AmtB is required for GlnK association. Whole-cell extracts (W), and cytoplasmic (C) and membrane (M) fractions were prepared from strain GT1000 (pGC4) [ΔglnK amtB (glnK amtB4)] both before (–N) and after (AS) ammonia shock. Extracts and fractions were prepared as described in Materials and methods and were subjected to SDS–PAGE followed by western blotting using an anti-P_II antibody.