Direct energy transfer to study the 3D structure of non-native proteins: AGH complex in molten globule state of apomyoglobin

The direct energy transfer technique was modified and applied to probe the relative localization of apomyoglobin A-, G- and H-helixes, which are partl y protected from deuterium exchange in the equilibrium molten globule state and in the molten globule-like kinetic intermediate. The non-radiative tra nsfer of tryptophan electronic energy to 3-nitrotyrosine was studied in dif ferent conformational states of apomyoglobin (native, molten globule, unfol ded) and interpreted in terms of average distances between groups of the pr otein chain. The experimental data show that the distance between the middl e of A-helix and the N-terminus of G-helix as well as the distance between the middle of the A-helix and the C-terminus of the H-helix in the molten g lobule state are close to those in the native state. This is a strong argum ent in favor of similarity of the overall architecture of the molten globul e and native states.