Lab-Made 'Miniproteins' Could Block the Coronavirus from Infecting Cells | Virus World | Scoop.it
From www.scientificamerican.com - October 12, 2020 11:15 AM

Scientific American is the essential guide to the most awe-inspiring advances in science and technology, explaining how they change our understanding of the world and shape our lives. While the world waits for a COVID-19 vaccine, many researchers are focused on developing effective therapeutics that can be rolled out quickly and cheaply. Monoclonal antibodies—a potentially promising laboratory-manufactured therapy modeled on antibodies extracted from the blood of recovering patients—made headlines recently when President Trump received a not-yet-approved antibody cocktail made by the company Regeneron. And pharmaceutical giant Eli Lilly recently announced that its monoclonal antibody reduced the risk of hospitalization in 300 people who had mild or moderate symptoms of COVID-19, in a small clinical trial. But David Baker, a biochemist at the University of Washington’s Institute for Protein Design, and his colleagues think they can produce an even better therapy. They have designed a synthetic peptide—a short string of amino acids, the building blocks of proteins—20 times smaller than a monoclonal antibody that is designed to bind to the infamous “spike” protein on the surface of the SARS-CoV-2 virus particle. Doing so would directly block the virus from binding to the ACE-2 receptors on human cells, functioning much like an antibody produced by an infected person’s immune system. Baker and his colleagues described these “miniprotein inhibitors” in September in Science. Although the study only tested these synthetic proteins in the lab, mixing viral particles with monkey cells in vitro, he says that unpublished data show they can protect mice and hamsters from SARS-CoV-2 infection. 

 

“We built these [tiny proteins] from scratch based on ‘first principles,’ using computers to model all the biochemical details of a theoretical protein that could stick to the virus,” explains Baker, who was awarded a $3 million Breakthrough Prize earlier in September for his decades of work pioneering the field of synthetic protein design. His team used computers to digitally design more than two million candidate “miniproteins,” crunched the data using algorithms, sifted out 118,000 candidate genes that encode these proteins, manufactured the proteins from scratch, and tested them directly against the virus in the lab—finding that seven designs could effectively bind to and thus disable the virus. Over the course of 3.5 billion years evolution has produced an incredible array of proteins and peptides. In recent years biochemists have tracked down and used some of these to create new drugs, such as Eptifibatide, an antiplatelet drug administered to prevent heart attacks whose active ingredient is extracted from the venom of the southern pygmy rattlesnake. The Protein Data Bank, an online repository of protein sequences and educational tools, contains the amino acid sequences and full 3-D structures for more than 160,000 peptides and proteins—but the natural world contains hundreds of millions of proteins. 

 

“It’s very challenging to discover in nature a peptide that does exactly what you want it to do,” explains Gaurav Bhardwaj, also a biochemist at the Institute for Protein Design, but who was not involved in the Science study. He is trying to design a bespoke peptide that would prevent SARS-CoV-2 from replicating within human cells. “Now we can computationally explore the possible design configurations for a peptide in order to perform the exact functions that we want.” Every protein’s function depends on its structure. Interactions between the atoms of the protein’s amino acids cause these chains to self-assemble in less than a second into a complex array of spirals and pleats. As the chain of amino acids grows, these helices and rippled sheets stack on top of and around one another into a dizzyingly complex series of folds, and it is these folds that give proteins their shape and function. Yet figuring out how one amino acid sequence turns into a specific fold has been a torturously difficult task, and it was only in the 1990s—with ever expanding databases of protein information—that scientists could begin to link sequence to form. “We can make up completely new proteins that have never been seen in nature because we now understand the nature of protein folding,” Baker says. “Our ability to use computers to design ‘de novo’ proteins has really only come into its own in the last few years–we might not have been able to apply ourselves to COVID-19 if the pandemic had happened five years ago....