Large pore gels to separate mega protein complexes larger than 10 MDa by blue native electrophoresis: Isolation of putative respiratory strings or patches

Here, we expand the application of blue native electrophoresis to the separation of mega protein complexes larger than 10 MDa by introducing novel large pore acrylamide gels. We tailored the bis-acrylamide cross-linker amounts relative to the acrylamide monomer to enlarge the pore size of acrylamide gels and to obtain elastic and sufficiently stable gels. The novel gel types were then used to search for suprastructures of mitochondrial respiratory supercomplexes, the hypothetical respiratory strings, or patches. We identified 4-8 MDa assemblies that contain respiratory complexes I, III, and IV and most likely represent dimers, trimers, and tetramers of respiratory supercomplexes. We also isolated multimeric respiratory supercomplexes with apparent masses of 35-45 MDa, the presumed core pieces of respiratory strings or patches. Electron microscopic investigations will be required to clarify whether the isolated assemblies of complexes are ordered and specific, as predicted for respiratory strings and patches in the mitochondrial membrane.