Figure 2.

Comparison of native ESI mass spectra of WT-NAC and ΔUBA-NAC. a and b, native ESI mass spectra of WT-NAC (a) and ΔUBA-NAC (b). Each spectrum shows two charge-state distributions for each heterodimer (green and red for WT-NAC and ΔUBA-NAC, respectively), with low populations of α₂β₂-NAC dimers as indicated. In addition, low populations of dissociated α-NAC and β-NAC subunits are observed (blue). The insets show the proteins analyzed by native PAGE, which reveal a single band of the heterodimer and no evidence of dissociation. c, estimated collision cross-sections (CCS) from ESI-IMS-MS experiments for WT-NAC (green circles) and ΔUBA-NAC (red triangles) show that compact and extended forms co-exist for both species (see also Table S1). d, far-UV CD spectra of WT-NAC (green) and ΔUBA-NAC (red). The secondary structure content obtained using CONTIN (58) is given in Table S2.