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Geobacter nanowire structure surprise.
F Wang, Y Gu, JP O'Brien, SM Yi, SE Yalcin, V Srikanth, C Shen, D Vu, NL Ing, AI Hochbaum, EH Egelman, NS Malvankar. Cell 2019 doi: 10.1016/j.cell.2019.03.029 Bacteria living in anaerobic environments (no oxygen) need alternative electron acceptors in order to get energy from their food. An acceptor abundant in the earth's crust is red iron oxide ("rust"), which gets reduced to black iron oxide (magnetite). Many bacteria, such as Geobacter, get their metabolic energy by transferring electrons to acceptors that are multiple cell diameters distant, using protein nanowires. These were long thought to be pili. But when the structure of the nanowires was solved in 2019, to everyone's surprise, they turned out to be unprecedented linear polymers of multi-heme cytochromes. The hemes form an electrically conductive chain in the cores of these nanowires.
by Eric Martz
After decades of slow progress by many groups, in 2020, AlphaFold2 proved able to accurately predict the detailed structures of two-thirds of single protein domains from their amino acid sequences. Pictured is AlphaFold2's prediction for the ORF8 protein of SARS-CoV-2 (black), compared with a subsequently published X-ray crystallographic structure (colors). ORF8 contributes to virulence in COVID-19.
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Tutorial: The Ramachandran principle, phi (φ) and psi (ψ) angles in proteins
by Eric Martz
The Ramachandran Principle says that alpha helices, beta strands, and turns are the most likely conformations for a polypeptide chain to adopt, because most other conformations are impossible due to steric collisions between atoms.
Check Show Clashes to see where non-bonded atoms are overlapping, and thus in physically impossible positions.