M1 protein

The M1 protein is a matrix protein of the influenza virus. It forms a coat inside the viral envelope.

The M1 protein binds to the viral RNA. The binding is not specific to any RNA sequence, and is performed via a peptide sequence rich on basic aminoacids.

It also has multiple regulatory functions, performed by interaction with the components of the host cell. The mechanisms regulated include the export of the viral ribonucleoproteins from the host cell nucleus, inhibition of viral transcription, and plays a role in the virus assembly and budding. The protein was found to undergo phosphorylation in the host cell.

The M1 protein forms a layer under the patches of host cell membrane that are rich with the viral hemagglutinin, neuraminidase and M2 transmembrane proteins, and facilitates budding of the mature viruses.