M1 protein

{{Infobox protein family

| Symbol = Flu_M1

| Name = Flu_M1

| image = PDB 1ea3 EBI.jpg

| width =

| caption = influenza virus m1 protein

| Pfam = PF00598

| Pfam_clan =

| InterPro = IPR001561

| SMART =

| PROSITE =

| MEROPS =

| SCOP = 1aa7

| TCDB =

| OPM family = 42

| OPM protein = 1aa7

| CAZy =

| CDD =

}}

The M1 protein is a matrix protein of the influenza virus. It forms a coat inside the viral envelope. This is a bifunctional membrane/RNA-binding protein that mediates the encapsidation of nucleoprotein cores into the membrane envelope. It is therefore required that M1 binds both membrane and RNA simultaneously.{{cite journal |vauthors=Sha B, Luo M | title = Structure of a bifunctional membrane-RNA binding protein, influenza virus matrix protein M1 | journal = Nat. Struct. Biol. | volume = 4 | issue = 3 | pages = 239–44 |date=March 1997 | pmid = 9164466 | doi = 10.1038/nsb0397-239| s2cid = 22521750 }}

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 in basic amino acids.{{cn|date=August 2022}}

It also has multiple regulatory functions, performed by interaction with the components of the host cell. The mechanisms regulated include a role in the export of the viral ribonucleoproteins from the host cell nucleus, inhibition of viral transcription, and a role in the virus assembly and budding. The protein was found to undergo phosphorylation in the host cell.{{cn|date=August 2022}}

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.{{cn|date=August 2022}}

M1 consists of two domains connected by a linker sequence. The N-terminal domain has a multi-helical structure that can be divided into two subdomains.{{cite journal |vauthors=Arzt S, Baudin F, Barge A, Timmins P, Burmeister WP, Ruigrok RW | title = Combined results from solution studies on intact influenza virus M1 protein and from a new crystal form of its N-terminal domain show that M1 is an elongated monomer | journal = Virology | volume = 279 | issue = 2 | pages = 439–46 |date=January 2001 | pmid = 11162800 | doi = 10.1006/viro.2000.0727 | doi-access = free }} The C-terminal domain also contains alpha-helical structure.