Mitochondrial ATP synthases form dimers, which assemble into long ribbons at the rims of the inner membrane cristae. We reconstituted detergent-purified mitochondrial ATP synthase dimers from the green algaePolytomellasp. and the yeastYarrowia lipolyticainto liposomes and examined them by electron cryotomography. Tomographic volumes revealed that ATP synthase dimers from both species self-assemble into rows and bend the lipid bilayer locally. The dimer rows and the induced degree of membrane curvature closely resemble those in the inner membrane cristae. Monomers of mitochondrial ATP synthase reconstituted into liposomes do not bend membrane visibly and do not form rows. No specific lipids or proteins other than ATP synthase dimers are required for row formation and membrane remodelling. Long rows of ATP synthase dimers are a conserved feature of mitochondrial inner membranes. They are required for cristae formation and a main factor in mitochondrial morphogenesis.

SignificanceOxygenic phosphorylation entails the transfer of electrons from organic substrates to molecular oxygen by four large protein complexes in the mitochondrial inner membrane. Loss of electrons during this process can produce toxic side products and must be prevented. Three of the electron-transfer complexes form supercomplexes, which are thought to be instrumental in channeling electrons from the substrate to the acceptor. We used electron cryo-tomography and subtomogram averaging to determine the in situ structure and organization of the respiratory chain supercomplexes in three different eukaryotic lineages. We discovered that the mutual arrangement of the two largest components—complex I and complex III2—is essentially the same in all supercomplexes, indicating that this arrangement is important for electron transfer.

The successful integration of 2D nanomaterials into functional devices hinges on developing fabrication methods that afford hierarchicalcontrol across length scales of the entire assembly.W ed emonstrate structural control over ac lass of crystalline 2D nanosheets assembled from collagen triple helices.Bylengthening the triple helix unit through sequential additions of Pro-Hyp-Gly triads,w ea chieved sub-angstrom tuning over the 2D lattice.T hese subtle changes influence the overall nanosheet size, which can be adjusted across the mesoscale size regime.The internal structure was observed by cryo-TEM with direct electron detection, whichprovides realspace high-resolution images,inwhich individual triple helices comprising the lattice can be clearly discerned. These results establish ag eneral strategy for tuning the structural hierarchy of 2D nanomaterials that employr igid, cylindrical structural units.

Engineering free-standing 2D nanomaterials with compositional, spatial, and functional control across size regimes from the nano- to mesoscale represents a significant challenge. Herein, we demonstrate a straightforward strategy for the thermodynamically controlled fabrication of multicomponent sectored nanosheets in which each sector can be chemically and spatially addressed independently and orthogonally. Collagen triple helices, comprising collagen-mimetic peptides (CMPs), are employed as molecularly programmable crystallizable units. Modulating their thermodynamic stability affords the controlled synthesis of 2D core–shell nanostructures via thermally driven heteroepitaxial growth. Structural information, gathered from SAXS and cryo-TEM, reveals that the distinct peptide domains maintain their intrinsic lattice structure and illuminates various mechanisms employed by CMP triple helices to alleviate the elastic strain associated with the interfacial lattice mismatch. Finally, we demonstrate that different sectors of the sheet surface can be selectively functionalized using bioorthogonal conjugation chemistry. Altogether, we establish a robust platform for constructing multifunctional 2D nanoarchitectures in which one can systematically program their compositional, spatial, and functional properties, which is a significant step toward their deployment into functional nanoscale devices.

Amyloid-b peptide (Ab)o ligomers are pathogenic species of amyloid aggregates in Alzheimersd isease.L ike certain protein toxins,A b oligomers permeabilizec ellular membranes,p resumably through ap ore formation mechanism. Owing to their structural and stoichiometric heterogeneity,the structure of these pores remains to be characterized. We studied af unctional Ab42-pore equivalent, created by fusing Ab42 to the oligomerizing,s oluble domain of the ahemolysin (aHL) toxin. Our data reveal Ab42-aHL oligomers to share major structural, functional, and biological properties with wild-type Ab42-pores.Single-particle cryo-EM analysis of Ab42-aHL oligomers (with an overall 3.3 resolution) reveals the Ab42-pore region to be intrinsically flexible.T he Ab42-aHL oligomers will allow many of the features of the wild-type amyloid oligomers to be studied that cannot be otherwise,a nd mayb eah ighly specific antigen for the development of immuno-base diagnostics and therapies.