Daneshparvar, N. | bioRxiv Science

bioRxiv2021

Distinct cryo-EM Structure of α-synuclein Filaments derived by Tau

Recent structural studies of ex vivo amyloid filaments extracted from human patients demonstrated that the ex vivo filaments associated with different disease phenotypes adopt diverse molecular conformations distinct from those in vitro amyloid filaments. A very recent cryo-EM structural study also revealed that ex vivo -synuclein filaments extracted from multiple system atrophy (MSA) patients adopt quite distinct molecular structures from those of in vitro -synuclein filaments, suggesting the presence of co-factors for -synuclein aggregation in vivo. Here, we report structural characterizations of -synuclein filaments derived by a potential co-factor, tau, using cryo-EM and solid-state NMR. Our cryo-EM structure of the tau-promoted -synuclein filament at 4.0 [A] resolution is somewhat similar to one of the polymorphs of in vitro -synuclein filaments. However, the N- and C-terminal regions of the tau-promoted -synuclein filament have different molecular conformations. Our structural studies highlight the conformational plasticity of -synuclein filaments, requiring additional structural investigation of not only more ex vivo -synuclein filaments, but also in vitro -synuclein filaments formed in the presence of diverse co-factors to better understand molecular basis of diverse molecular conformations of -synuclein filaments.

biochemistry↗

bioRxiv2020

CryoEM Structure of Drosophila Flight Muscle Thick Filaments at 7A Resolution

Striated muscle thick filaments are composed of myosin II and several non-myosin proteins. Myosin IIs long -helical coiled-coil tail forms the dense protein backbone of filaments while its N-terminal globular head containing the catalytic and actin binding activities extends outward from the backbone. Here we report the structure of thick filaments of the flight muscle of the fruit fly Drosophila melanogaster at 7 [A] resolution. Its myosin tails are arranged in curved molecular crystalline layers identical to flight muscles of the giant waterbug Lethocerus indicus. Four non-myosin densities are observed, three of which correspond to ones found in Lethocerus; one new density, possibly stretchin-Mlck, is found on the backbone outer surface. Surprisingly, the myosin heads are disordered rather than ordered along the filament backbone. Our results show striking myosin tail similarity within flight muscle filaments of two insect orders separated by several hundred million years of evolution. Significance StatementMyosin thick filaments are one of striated muscles key structures, but also one of its least understood. A key question is how the myosin a-helical coiled-coil tail is arranged in the backbone. At 7[A] resolution, sufficient to resolve individual a-helices, the myosin tail arrangement in thick filaments from the flight muscle of the fruit fly Drosophila melanogaster is strikingly similar to the myosin tail arrangement in flight muscles of the giant waterbug Lethocerus indicus. Nearly every other thick filament feature is different. Drosophila and Lethocerus evolved separately >245 million years ago suggesting myosin tail packing into curved molecular crystalline layers forms a highly conserved thick filament building block and different properties are obtained by alterations in non-myosin proteins.

biophysics↗