Lecture 22

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University of Toronto St. George
Cell and Systems Biology
Mounir Abou Haidar

Lec22 Nov 27 Proof 918Lets continue with influenza enveloped virus Pg 136 8 Properties of Viral Proteins926Hemagglutinin HA and Neuraminidase NA are glycoproteins on the surface of the envelope of this virus The lipid portion of the envelope is from the infected cells membrane This virus codes for its own glycoprotein The Neuraminidase NA is a receptor binding site This site recognizes sialic acid molecules on the surface of the cells in the respiratory tract This allows influenza to recognize respiratory cells via NA Influenza attaches to the respiratory cells via HA NA is a very large glycoproteinPost translational modification extra modification that occurs after the protein has translated oHA modificationsst1 the protein trimerizes 3 identical subunits attach to each other and make a trimer nd2 The trimer gets glycosylated sugar attachesrd3 They then form disulfide bond through cysteinecysteine SS bond th4 Palmitoylationthey add palmitilic acid oil after on surface of HA glycoproteinDefn Palmitoylation is the covalent attachment of fatty acids such as palmitic acid to cysteine residues of membrane proteinsth5 Proteolytic cleavage some pieces of HA get cleavedlead to conformation change of the protein oMain functions of HA areAttaches to the receptor of the host cell It has fusion activitymeans the HA attaches to the membrane of the host cell and will help fuse the envelope of the virus with the membrane of the cell to allow the virus to enter the cell many viruses have a fusion protein we will learn HA is a large protein and has many functionsNow when the virus gets in the host through the fusion protein HA in this case the proton pump which is Matrix 2 M2 protein saw last class ON TESTMatrix 2 protein is a proton pump protein which is on the surface of the virus oThis M2 protein crosses the membrane ie the envelope of the virus connecting the inside of the virus with the outside of the virus oThe M2 protein sucks H ions from the outside environment and dumps them inside the virusto acidify the virus Once the virus is acidified it will dissociate from the envelope UNCOAT to dump its RNA in the host to start viral replication once have acidification in the endosome it will induce a conformational change in the HAPg 135 Diagram of Influenza virus 1355He points out the M2 protein on the surface of the virus ie the M2 protein
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