S T R U C T U R A L B I O L O G Y

S C I E N T I F I C H I G H L I G H T S

4 4 H I G H L I G H T S 2 0 2 2 I

Amyloid and hydrogel formation of a peptide sequence from a coronavirus spike protein

A coronavirus spike protein fragment (peptide) forms amyloid structures, fibre-like dysfunctional protein aggregates that are characteristic of a range of diseases. The pH-dependent structure of a short peptide common to many animal and human coronavirus spike proteins was investigated. Synchrotron small-angle X-ray scattering in combination with other methods showed that, under very specific pH conditions, the peptide forms unexpected amyloid structures.

The COVID-19 pandemic has stimulated immense

research activity into the SARS-CoV-2 coronavirus spike protein and its fusion process with human cells. The sequence of this protein has been determined and key regions involved in the binding of the spike glycoprotein have been identified, in the context of determining potential targets for therapeutic intervention. The peptide RSAIEDLLFDKV is found in many coronaviruses including the human common cold coronavirus spike protein as well as other coronavirus spike proteins from other animals [1]. It immediately follows the second (S2) cleavage site in SARS-CoV and MERS-CoV, and closely related sequences identified in SARS-CoV-2 [1]. The structure of a coronavirus protein containing the single-residue substitution sequence RSAIEDLLFNKV was determined by cryo-electron microscopy (Figure 35).

The pH-dependent self-assembly and gelation of peptide RSAIEDLLFDKV was investigated. This peptide has an expected pI = 4.2. Amyloid structures are characterised by β-sheet secondary structure. This is unexpected for RSAIEDLLFDKV, since closely related sequences lie in coil regions of the spike S2 domain surface (Figure 35), and, in addition, amyloid aggregation tendency web algorithms inaccurately predict that this sequence does not form β-sheet structures.

Possible amyloid formation by RSAIEDLLFDKV was investigated using small-angle X-ray scattering

Fig. 35: Structure of a porcine coronavirus spike protein, obtained from high-resolution cryo-EM. The sequence RSAIEDLLFNKV is highlighted (in red). This is the closest sequence to RSAIEDLLFDKV for which a PDB file could be obtained. The spike has a trimeric structure. Top: side and top views, bottom: enlargement of RSAIEDLLFNKV region with residue numbers for the A chain. The peptide clearly lies in a surface coil sequence.

The present study reveals the role played by MQ in stabilising p53 and its interaction with DNA, thus providing a structural framework for the design of new

drug molecules to target specific p53 cysteines for potential cancer therapy.

PRINCIPAL PUBLICATION AND AUTHORS

Structural basis of reactivation of oncogenic p53 mutants by a small molecule: methylene quinuclidinone (MQ), O. Degtjarik (a,d), D. Golovenko (a,e), Y. Diskin-Posner (b), L. Abrahmsén (c), H. Rozenberg (a), Z. Shakked (a), Nat. Commun. 12(1), 7057 (2021); https:/doi.org/10.1038/s41467- 021-27142-6 (a) Department of Chemical and Structural Biology, Weizmann Institute of Science (Israel) (b) Department of Chemical Research Support, Weizmann Institute of Science (Israel) (c) Aprea Therapeutics AB (Sweden) (d) Present address: Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, University of Leeds (UK) (e) Present address: University of Massachusetts Medical School, RNA Therapeutics Institute, Worcester, MA (USA)

REFERENCES

[1] M. Kitayner et al., Mol. Cell. 22(6), 741-753 (2006). [2] M. Kitayner et al., Nat. Struct. Mol. Biol. 17, 423-429 (2010). [3] D. Golovenko et al., Structure 26(9), 1237-1250 (2018). [4] O. Suad et al., J. Mol. Biol. 385, 249-265 (2009). [5] A. Eldar et al., Nucleic Acids Res. 41, 8748-8759 (2013).