NCI scientists image proteins displayed on HIV surface
Using a technique called cryo-electron microscopy, researchers at the National Cancer Institute (NCI) have been able to detect shape changes in a protein called Env that is part of HIV (the human immunodeficiency virus). HIV infection is initiated when Env binds to receptors on host cells. The finding appeared in the July 12, 2012, issue of PLoS Pathogens. To carry out their study, NCI scientists studied both intact HIV viruses and purified Env proteins. The HIV and protein samples were flash-frozen to very low temperatures using methods that preserve their structure and prevent formation of crystalline ice. The frozen samples were then imaged using an electron microscope. By compiling images of the proteins viewed from many different angles, the scientists were able to construct 3-dimensional models of Env and determine the changes it undergoes when it gets activated to enter host cells.
The imaging of the HIV Env protein in its activated state revealed three helical rods at its base. Because these regions of Env are derived from amino acids that are highly conserved across most HIV strains, the researchers hypothesize that development of antibodies that target this newly discovered structure could provide effective strategies to block HIV infection by attacking it at a highly vulnerable state prior to its entry into a cell. To read more about research from this lab, please go to http://electron.nci.nih.gov.
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