Extended Data Fig. 4: NMR analysis of the BAX/CBI1 interaction.
a, Measured chemical shift changes of 15N-BAX (20 μM) upon addition of CBI1 (5:1 of CBI1:BAX), plotted as a function of BAX residue number. Chemical shift changes above the 2 s.d. cutoff (significance threshold of 0.0536 p.p.m.) are colored maroon and those above the 1 s.d. cutoff (significance threshold of 0.0347 p.p.m.) are colored red. Residues whose cross peaks experienced prominent signal attenuation or chemical shift perturbation upon CBI1 incubation are colored beige. b-c, Chemical shift perturbations of BAX cross peaks corresponding to residues F116 (b, dashed box) and S118 (c) upon addition of CBI1. Whereas BAX exhibited one cross peak each for F116 and S118 (gray), the addition of CBI1 at a CBI1:BAX ratio of 5:1 resulted in the appearance of a second cross peak for each residue (red). Upon incubation with CBI1 at a CBI1:BAX ratio of 10:1, the original cross peaks shifted completely to the second locations (blue). In contrast, D142 (b) experienced little to no change in its corresponding cross peak upon addition of CBI1. d, Prominent signal attenuation or chemical shift perturbation of A81 in wild-type BAX upon CBI1 titration, as reflected by disappearance of the cross peak. e, In contrast, in the context of BAX C126A, the A81 cross peak demonstrates progressive migration upon CBI1 titration, consistent with fast exchange between the unbound and bound forms of BAX C126A, as expected for non-covalent interaction.
