FIG. 2.

Cold-chase ATP labeling of L. monocytogenes HPr. Fractions of ³²P-labeled HPr were removed at various times, as indicated, following addition of 5 mM nonradioactive ATP: lane 1, 0 min; lane 2, 2 min; lane 3, 10 min; lane 4, 20 min; lane 5, 30 min; lane 6, 45 min; lane 7, 1 h; lane 8, 1.5 h; lane 9, 16 h. Results were identical for samples exposed to L. monocytogenes whole-cell extracts or cellular membranes. In certain cases, excess [γ-³²P]ATP was removed (via Sephadex G-50 spin columns) in lieu of addition of 5 mM nonradioactive ATP. In such cases, results were identical to those displayed regardless of the presence or absence of sodium phosphate (25 mM).