Recently, researchers at the University of Illinois in Chicago analyzed the crystal structure of an enzyme derived from a virus that causes SARS (severe acute respiratory syndrome) and can be used as a new drug target against SARS. By revealing the three-dimensional structure of this papain-like protease (PLpro), researchers can use their molecular maps to design new drugs to treat SARS-infected patients, or SARS-related diseases such as the common cold, bronchitis, or pneumonia. Researchers are also trying to use the same method to design effective drugs against HIV protease, and then develop new drugs to fight AIDS virus. The results of the study were published in the "Proceedings of the National Academy of Sciences" published on March 27. This study reports for the first time on this level of protease structure, which is expected to treat patients infected with coronavirus that can cause SARS. As early as the 1960s, researchers discovered that coronavirus can cause upper respiratory tract infections and that 10-30% of common colds are caused by the virus. Recently, researchers have discovered that two new coronaviruses (NL63 and HKU1) can cause severe pneumonia in children and the elderly. Severe infections with NL63 and HKU1 viruses usually require hospitalization, and recent new technologies can detect these viruses. Papaya-like proteases are the most basic conditions for the replication and infection of all coronaviruses that infect the upper respiratory tract. Removal of these enzymes prevents further infections. Currently, researchers have discovered compounds that bind the pockets of these proteins and inhibit the activity of these enzymes. The next step is to develop drugs that counteract this enzyme in the short term.