ИСТИНА

We have recently revealed the amphipathicity of six CRAC containing alpha-helices of influenza virus (IFV) M1 protein, and suggest that the phenomenon may play a role in supporting both raft structure of the membrane and organising regular structure the M1 protein shell in the virion [1]. Computer modelling and comparative analysing 3D structures of the matrix proteins was carried out for three taxonomically different enveloped viruses with raft-type membranes, IFV, Newcastle disease virus (NDV), and Human immunodeficiency virus (HIV), to disclose amphipathic CRAC containing 3D configurations in their structures, and to identify putative motifs, which may be specifically involved in their interactions with raft membranes. Common structural feature of all three proteins was found to be the amphipathic structure of their CRAC motifs, and localization of the outer CRAC regions on the opposite sides of their globules. Notably, in contrast to IFV M1, one CRAC motif on NDV M appeared on the amphipathic beta-sheet structure. To verify our approach we also comparatively tested the M protein structure of the non-raft vesicular stomatitis virus: the disclosed surface CRAC motif appeared no amphipathic configuration. Small-angle X-ray structural analysis (SAXS) of IFV and NDV matrix proteins in solution gave further evidence in support of our conclusions. M1 protein exists in solution as a monomer with a compact NM-fragment and an extended and partially flexible C-terminal domain. SAXS analysis demonstrates that CRAC motifs of the M1 protein are located on the opposite sides of the NM-fragment perpendicular to the C-domain. NDV M protein dimerizes in solution, and its surface CRAC motifs have anti-parallel location on the opposite sides of the dimer. Thus, such localization of CRAC motifs of two different proteins with two different organizations in solution allows these matrix proteins to interact both with the membrane and with the internal components of the virus. Moreover, our results suggest that oppositely situated CRAC motifs in pairs of both monomeric IFV M1 and dimeric NDV M in the virions may serve as anchors between two neighbouring raft platforms consolidating and fastening the envelopes of the viruses. CRAC motifs on the surface of these proteins may be involved in arranging their regular oligomeric structures both in the virions and in solution. This work was supported in part by Russian Foundation for Basic Researches (projects 15-54-74002 EMBL and 16-04-00563) References 1. T. Tsfasman, V. Kost, S. Markushin, V. Lotte, I. Koptiaeva, E. Bogacheva, L. Baratova, V. Radyukhin. Amphipathic alpha-helices and putative cholesterol binding domains of the influenza virus matrix M1 protein are crucial for virion structure organization, Virus Research, 2015, v. 210, pp. 114–118.