User talk:Eman AlaliSandbox 1: Difference between revisions

[[Image:The_change_of_Hemagglutinin_structure_and_subunits_arrangement_due_to_the_drop_of_PH_level.PNG|left|200px|thumb|Figure 4. The change of Hemagglutinin structure and subunits arrangement due to the drop of PH level. A) the separation of H1 bulbs due to the drop of pH level. B) the separation of H1 and H2.] ]]

When H protein attaches to sialic acid residues of the ciliated columnar epithelial cell lining the sinuses and airways, the bound virus is endocytosed by the cell and the virions enter the cell within the endosomal vesicle. Then the endosomal vesicle  pH level drops and reaches about 5.5 due to the pumping of protons inside the vesicle by the M2 ions channel. As a result,  the <scene name='SAndbox_159/Ha1/1'>H1</scene> subuint shifts its position, allowing the <scene name='SAndbox_159/Ha2/2'>H2</scene> subunit to become embedded in the host cell membrane. Additionally, the C-terminus embedded in the viral membrane rearranges, bringing the two membranes closer together and facilitation fusion (Wilson et. al 1981). The pH induced conformational changes are partially but not completely reversible. As the pH decrease to 5.5,  the three globular heads start to dissociate due to the protonation of relevant H protein residues. the change in pH facilitate the releasing of the fusion peptides. Also at low pH the short and long alpha-helix are separated(Thoennes et.al 2008). The shifting of  <scene name='SAndbox_159/Ha1/1'>H1</scene> subunit plays an important role in H mediated membrane fusion , <scene name='SAndbox_159/Ha1/1'>H1</scene> protein helps the membrane attachment and fusion, which results in the release of viral RNA’s into the cytoplasm and then into the cell’s nucleus for RNA replication (Racanilllo, 2009).