Figure 4. ADP.Vi-trapped MsbA with bound ADP-βS.

(a) Cross-polarized (CP) ³¹P-MAS NMR allows to observe bound ADP.Vi at −6.2 and −10.9 p.p.m. (right). Upon addition of excess of ADP-βS, an additional resonance at 34.5 p.p.m. corresponding to βP-ADP-βS is observed. Furthermore, the peak at −11.0 p.p.m. doubles because of the overlap of αP-ADP-βS and aP-ADP.Vi. Peak deconvolution reveals the same integral peak intensities for ADP-βS and ADP.Vi, indicative of a 1:1 stoichiometry. (b) Directly polarized ³¹P-MAS NMR spectra of MsbA in complex with ADP-βS and ADP.Vi shows that no γP-ATP-βSγS is produced as shown in Fig. 2. Spectra were recorded under the same conditions as described in the Methods. The nominal temperature in a was set to 260 K and in b to 270 K. SSB refers to spinning sideband.