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The genetic material of a virus is stored within a viral protein structure called the capsid. The capsid is a "shield" that protects the viral nucleic acids from getting degraded by host enzymes or other types of pesticides or pestilences. It also functions to attach the virion to its host, and enable the virion to penetrate the host cell membrane.
During assembly of the bacteriophage (phage) T4 virion, the structural proteins encoded by the phage genes interact with each other in a characteristic sequence. Maintaining an appropriate balance in the amounts of each of these structural proteins produced during viral infection appears to be critical for normal phage T4 morphogenesis. [4]
The proteins making up the capsid are called capsid proteins or viral coat proteins (VCP). The virus genomic component inside the capsid, along with occasionally present virus core protein, is called the virus core. The capsid and core together are referred to as a nucleocapsid (cf. also virion).
The p1 protein of Ff phage (i. e. genus Inovirus), which is required for phage assembly at the membrane, has a membrane-spanning hydrophobic domain with the N-terminal portion in the cytoplasm and the C-terminal portion in the periplasm (the reverse of the orientation of the gene 8 coat protein). Adjacent to the cytoplasmic side of the membrane ...
Each type of protein is a specialist that usually only performs one function, so if a cell needs to do something new, it must make a new protein. Viruses force the cell to make new proteins that the cell does not need, but are needed for the virus to reproduce. Protein synthesis consists of two major steps: transcription and translation. [34]
An example is the M1 protein of the influenza virus, showing affinity to the glycoproteins inserted in the host cell membrane on one side and affinity for the RNP complex molecules on the other side, which allows formation at the membrane of a complex made of the viral ribonucleoprotein at the inner side indirectly connected to the viral ...
When not inside an infected cell or in the process of infecting a cell, viruses exist in the form of independent viral particles, or virions, consisting of (i) genetic material, i.e., long molecules of DNA or RNA that encode the structure of the proteins by which the virus acts; (ii) a protein coat, the capsid, which surrounds and protects the ...
3D model of the flu virion. (M2 labeled in white.) The Matrix-2 (M2) protein is a proton-selective viroporin, integral in the viral envelope of the influenza A virus. The channel itself is a homotetramer (consists of four identical M2 units), where the units are helices stabilized by two disulfide bonds, and is activated by low pH.