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by Eric Martz
Black spots are mutations of concern in SARS-CoV-2 spike protein reported by UK scientists in December, 2020. RNA viruses mutate quickly so mutations are expected. These mutations may speed up contagion, but are unlikely to cause more severe COVID-19 and unlikely to reduce vaccine effectiveness. ACE2 binding residues. Animation shows priming via cleavage by furin.
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Y Gu, V Srikanth, AI Salazar-Morales, R Jain, JP O'Brien, SM Yi, RK Soni, FA Samatey, SE Yalcin, NS Malvankar. Nature 2021 doi: 10.1038/s41586-021-03857-w
Geobacter pili were long thought to be electrically conductive protein nanowires composed of PilA-N. Nanowires are crucial to the energy metabolism of bacteria flourishing in oxygen-deprived environments. To everyone's surprise, in 2019, the long-studied nanowires were found to be linear polymers of multi-heme cytochromes, not pili. The first cryo-EM structure of pili (2021) reveals a filament made of dimers of PilA-N and PilA-C, shown. Electrical conductivity of pili is much lower than that of cytochrome nanowires. Evidence suggests that PilA-NC filaments are periplasmic pseudopili crucial for exporting cytochrome nanowires onto the cell surface, rather than the pili serving as nanowires themselves.

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This tutorial illustrates some basic properties of protein structure:

• Levels of protein structure.
• Ways of representing protein structure.
• Secondary structures.
• Motifs in proteins.
• Domains.
• Tertiary structure.
• Quaternary structure.

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