Effect of the Coat Protein N-Terminal Domain Structure on the Structure and Physicochemical Properties of Virions of Potato Virus X and Alternanthera Mosaic Virus

---

Alexander L. Ksenofontov^1,a*, Maxim V. Petoukhov^2,3, Vladimir V. Matveev², Natalia V. Fedorova¹, Pavel I. Semenyuk¹, Alexander M. Arutyunyan¹, Tatiana I. Manukhova⁴, Ekaterina A. Evtushenko⁴, Nikolai A. Nikitin⁴, Olga V. Karpova⁴, and Eleonora V. Shtykova²

¹Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia

²Shubnikov Institute of Crystallography, Federal Scientific Research Centre “Crystallography and Photonics”, Russian Academy of Sciences, 119333 Moscow, Russia

³Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, 119071 Moscow, Russia

⁴Faculty of Biology, Lomonosov Moscow State University, 119234 Moscow, Russia

^* To whom correspondence should be addressed.

Received October 16, 2022; Revised November 17, 2022; Accepted November 19, 2022

---

The amino acid sequences of the coat proteins (CPs) of the potexviruses potato virus X (PVX) and alternanthera mosaic virus (AltMV) share ~40% identity. The N-terminal domains of these proteins differ in the amino acid sequence and the presence of the N-terminal fragment of 28 residues (ΔN peptide) in the PVX CP. Here, we determined the effect of the N-terminal domain on the structure and physicochemical properties of PVX and AltMV virions. The circular dichroism spectra of these viruses differed significantly, and the melting point of PVX virions was 10-12°C higher than that of AltMV virions. Alignment of the existing high-resolution 3D structures of the potexviral CPs showed that the RMSD value between the C_α-atoms was the largest for the N-terminal domains of the two compared models. Based on the computer modeling, the ΔN peptide of the PVX CP is fully disordered. According to the synchrotron small-angle X-ray scattering (SAXS) data, the structure of CPs from the PVX and AltMV virions differ; in particular, the PVX CP has a larger portion of crystalline regions and, therefore, is more ordered. Based on the SAXS data, the diameters of the PVX and AltMV virions and helix parameters in solution were calculated. The influence of the conformation of the PVX CP N-terminal domain and its position relative to the virion surface on the virion structure was investigated. Presumably, an increased thermal stability of PVX virions vs. AltMV is provided by the extended N-terminal domain (ΔN peptide, 28 amino acid residues), which forms additional contacts between the adjacent CP subunits in the PVX virion.

---

KEY WORDS: potexviruses, potato virus X, alternanthera mosaic viruses, coat protein, N-terminal domain, circular dichroism, small-angle X-ray scattering

DOI: 10.1134/S0006297923010108

---