The M1 protein is a matrix protein

Matrix protein

Viral matrix proteins are non structural proteins linking the viral envelope with the virus core. They play a crucial role in virus assembly, and interact with the RNP complex as well as with the viral membrane...

 of the influenza

Influenza

Influenza, commonly referred to as the flu, is an infectious disease caused by RNA viruses of the family Orthomyxoviridae , that affects birds and mammals...

 virus

Virus

A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...

. It forms a coat inside the viral envelope

Viral envelope

Many viruses have viral envelopes covering their protein capsids. The envelopes typically are derived from portions of the host cell membranes , but include some viral glycoproteins. Functionally, viral envelopes are used to help viruses enter host cells...

.

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

Peptide

Peptides are short polymers of amino acid monomers linked by peptide bonds. They are distinguished from proteins on the basis of size, typically containing less than 50 monomer units. The shortest peptides are dipeptides, consisting of two amino acids joined by a single peptide bond...

 sequence rich in basic

Base (chemistry)

For the term in genetics, see base A base in chemistry is a substance that can accept hydrogen ions or more generally, donate electron pairs. A soluble base is referred to as an alkali if it contains and releases hydroxide ions quantitatively...

 amino acid

Amino acid

Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...

s.

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 ribonucleoprotein

Ribonucleoprotein

Ribonucleoprotein is a nucleoprotein that contains RNA, i.e. it is an association that combines ribonucleic acid and protein together. A few known examples include the ribosome, the enzyme telomerase, vault ribonucleoproteins, and small nuclear RNPs , which are implicated in pre-mRNA splicing and...

s from the host cell nucleus

Cell nucleus

In cell biology, the nucleus is a membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes. The genes within these...

, inhibition of viral transcription

Transcription (genetics)

Transcription is the process of creating a complementary RNA copy of a sequence of DNA. Both RNA and DNA are nucleic acids, which use base pairs of nucleotides as a complementary language that can be converted back and forth from DNA to RNA by the action of the correct enzymes...

, and a role in the virus assembly and budding

Budding

Budding is a form of asexual reproduction in which a new organism grows on another one. The new organism remains attached as it grows, separating from the parent organism only when it is mature. Since the reproduction is asexual, the newly created organism is a clone and is genetically identical...

. The protein was found to undergo phosphorylation

Phosphorylation

Phosphorylation is the addition of a phosphate group to a protein or other organic molecule. Phosphorylation activates or deactivates many protein enzymes....

 in the host cell.

The M1 protein forms a layer under the patches of host cell membrane that are rich with the viral hemagglutinin

Hemagglutinin

Influenza hemagglutinin or haemagglutinin is a type of hemagglutinin found on the surface of the influenza viruses. It is an antigenic glycoprotein. It is responsible for binding the virus to the cell that is being infected...

, neuraminidase

Neuraminidase

Neuraminidase enzymes are glycoside hydrolase enzymes that cleave the glycosidic linkages of neuraminic acids. Neuraminidase enzymes are a large family, found in a range of organisms. The most commonly known neuraminidase is the viral neuraminidase, a drug target for the prevention of the spread...

 and M2

M2 protein

The M2 protein is a proton-selective ion channel protein, integral in the viral envelope of the influenza A virus. The channel itself is a homotetramer , where the units are helices stabilized by two disulfide bonds...

 transmembrane protein

Transmembrane protein

A transmembrane protein is a protein that goes from one side of a membrane through to the other side of the membrane. Many TPs function as gateways or "loading docks" to deny or permit the transport of specific substances across the biological membrane, to get into the cell, or out of the cell as...

s, and facilitates budding

Budding

Budding is a form of asexual reproduction in which a new organism grows on another one. The new organism remains attached as it grows, separating from the parent organism only when it is mature. Since the reproduction is asexual, the newly created organism is a clone and is genetically identical...

of the mature viruses.