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HIV-1 protease

by David Canner
The X-ray structure of HIV-1 protease reveals that it is composed of two symmetrically related subunits which form a tunnel where they meet. This is critical because it contains the active site of the protease, consisting on two Asp-Thr-Gly conserved sequences, making it a member of the aspartyl protease family. The two catalytic Asp's either interact with the incoming water or protonate the carbonyl to make the carbon more electrophilic for the incoming water.

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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.

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Polio is still here!
Polio vaccines have been available since the 1950s, but the challenges of vaccination in remote areas of Afghanistan and Pakistan have prevented worldwide eradication. In 2022, polio was found circulating in parts of New York State, USA. The polio virus has a small RNA genome enclosed in an icosahedral capsid composed of several proteins, shown cut in half. The structures of virus capsids can be explored using free FirstGlance in Jmol.

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