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bioRxiv · 10.1101/2021.02.01.429088

An unusual aspartic acid cluster in the reovirus attachment fiber σ1 mediates stability at low pH

Glorani, G.·Ruwolt, M.·Holton, N.·Neu, U.
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Abstract

The reovirus attachment protein {sigma}1 mediates cell attachment and receptor binding and is thought to undergo conformational changes during viral disassembly. {sigma}1 is a trimeric filamentous protein with an -helical coil-coiled Tail, a triple {beta}-spiral Body, and a globular Head. The Head domain features an unusual and conserved aspartic acid cluster at the trimer interface, which forms the only significant intra-trimer interactions in the Head, and must be protonated to allow trimer formation. Here we show that all domains of {sigma}1 are remarkably thermostable across a wide range of pH, even at the low pH of the stomach. Interestingly, we determine the optimal pH for stability to be between pH 5-6, a value close to the pH of the endosome and of the jejunum. The {sigma}1 Head is stable at acidic and neutral pH, but detrimerizes at basic pH. When Asp345 in the aspartic acid cluster is mutated to asparagine, the {sigma}1 Head loses stability at low pH and is more prone to detrimerize. Overall, the presence of the Body stabilizes the {sigma}1 Head. Our results confirm a role of the aspartic acid cluster as a pH-dependent molecular switch, and highlight its role in enhancing {sigma}1 stability at low pH.

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Glorani, G., Ruwolt, M., Holton, N., Neu, U.. 2021-02-01. An unusual aspartic acid cluster in the reovirus attachment fiber σ1 mediates stability at low pH. https://doi.org/10.1101/2021.02.01.429088

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