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Eric Martz
The first new influenza virus to emerge as an imminent pandemic threat in the 21st century is H1N1 swine flu. The drug oseltamivir (Tamiflu®) inhibits flu neuraminidase, a component necessary for virus spread, in susceptible flu strains. The development of oseltamivir was guided, in part, by crystallographically determined structures of flu neuraminidase, which is a homotetramer, shown with oseltamivir bound. Oseltamivir was designed to fit N2/N9 (neuraminidases from other strains of flu). Serendipitously, it also fits N1 by induced fit.

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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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The Capsid of a virus is its outer shell or "skin". Viruses have evolved intricate and elegant ways to assemble capsid protein chains into complete, usually spherical capsids, often with icosahedral symmetry. Pictured is an extremely simplified model of a capsid, where a single enlarged atom represents each of the 360 protein chains in the capsid of the Simian Virus 40 (SV40), a member of a group of cancer-causing viruses that has been extensively researched for decades.

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