Sunday, March 29, 2020

Researchers in China report structure of the novel coronavirus bound to its human target
Adapted from the news item in the Chemical & Engineering News (C&EN)1
The structure shows the first steps of SARS-CoV-2 infection, and could help in drug discovery
March 16, 2020

Chinese researchers have now identified part of the novel cornonavirus (SARS-CoV-2) bound to its target on human cells.  It binds to the angiotensin-converting enzyme (ACE2), an enzyme involved in blood pressure regulation.  Those of us who have high blood pressure, may be taking a a class of drugs called ACE-inhibitors (a common drug is lisinopril).  This discovery could lead to the development of antibodies that will block the interaction.  This knowledge is also used in developing vaccines that could prevent people from contracting the disease in future. 

More details from C&EN: ACE2 is the first in a string of enzymes that convert the hormone angiotensin into its active form. When cleaved by enzymes, angiotensin makes blood vessels contract. The SARS-CoV-2 spike protein has two key elements involved in infecting human cells. A string of amino acids in the S1 subunit directly binds to the protein-cleaving part of ACE2 called the peptidase domain. The S2 subunit of the spike protein helps the virus fuse to the human cell. The new structure shows the first of these two events. “You have attachment, and entry. Blocking either function can prevent entry,” Jason McLellan, a researcher from the University of Texas says, describing how treatments could be designed to stop SARS-CoV-2. “Ideally, you want antibodies that can target both functions.”

The scientists found that the protein-cleaving part of ACE2 binds the spike through polar interactions formed from a bridge-like structure on the enzyme. Both ends of the receptor binding domain stick to ACE2 through hydrogen bonding and van der Waals forces, and in the middle, Zhou describes several amino acids that interact with an asparagine and histidine in ACE2 that may be required for the spike protein-ACE2 interaction to occur.
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