One of the key steps in SARS infection occurs when a protein from the virus attaches to a receptor on the surface of a target host cell. Once attached, the virus fuses with the host cell and injects its RNA into the cell.
In this rendering, a protein fragment from the SARS virus, shown in blue and red, attaches to an ACE2 protein, which serves as the targeted host cell's receptor. The red area of the protein indicates the loop that contacts ACE2.
To determine the structure of the virus protein in complex with the host cell receptor, the complex was crystallized and then subjected to structural analysis using x-ray crystallography. With this technique, x-rays are directed through crystals of the protein complex. The resulting diffraction pattern is then analyzed to deduce the proteins' atomic structure.
The SARS (severe acute respiratory syndrome) coronavirus was responsible for a worldwide outbreak in 2002-2003 that affected more than 8,000 people and killed 774 before being brought under control.
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