January 2021 Archives

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Using HT-SAXS data collected at SIBYLS, Chris Brosey describes the value and versatility of Small Angle X-ray Scattering. Her article “Evolving SAXS versatility: solution X-ray scattering for macromolecular architecture, functional landscapes, and integrative structural biology” authored with John Tainer is among the top 10 most cited articles from Current Opinion in Structural Biology.

saxs endstation with title.pngSIBYLS is excited to announce we have a biochemist postdoc fellow opening. This is a great opportunity to work with experienced and innovative scientists in the field of structural biology. We are looking for someone who wants to develop and apply biology for multi-component biological macromolecules. You will be a part of a team that designs, develops, and applies synchrotron methods to characterize macromolecules and the assemblies they form. On top of all that, you will get an amazing, ever-changing view of the Bay, San Francisco skyline, and both the Golden Gate bridge and Bay bridges! For more information and to apply go here.

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The XRCC1-DNA ligase IIIα complex (XL) is critical for DNA single-strand break repair, a key target for PARP inhibitors in cancer cells deficient in homologous recombination. Here, we combined biophysical approaches to gain insights into the shape and conformational flexibility of the XL as well as XRCC1 and DNA ligase IIIα (LigIIIα) alone. Structurally-guided mutational analyses based on the crystal structure of the human BRCT-BRCT heterodimer identified the network of salt bridges that together with the N-terminal extension of the XRCC1 C-terminal BRCT domain constitute the XL molecular interface. Coupling size exclusion chromatography with small angle X-ray scattering and multiangle light scattering (SEC-SAXS-MALS), we determined that the XL is more compact than either XRCC1 or LigIIIα, both of which form transient homodimers and are highly disordered. The reduced disorder and flexibility allowed us to build models of XL particles visualized by negative stain electron microscopy that predict close spatial organization between the LigIIIα catalytic core and both BRCT domains of XRCC1. Together our results identify an atypical BRCT-BRCT interaction as the stable nucleating core of the XL that links the flexible nick sensing and catalytic domains of LigIIIα to other protein partners of the flexible XRCC1 scaffold.

Read more about it here.

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