Scientists at the University of California, Santa Cruz, discovered the virus that causes severe acute respiratory syndrome (SARS) has an unusual molecular structure that looks like a promising target for antiviral drugs, a UCSC press release said Monday.

In their article published by the journal PLoS Biology, scientists have determined the three-dimensional shape of this structure, an intricately twisted and folded segment of RNA. Their findings suggest that it may help the virus hijack the protein--building machinery of infected cells.

The SARS virus is a type of RNA virus, meaning that its genetic material is RNA rather than the more familiar DNA found in the chromosomes of everything from bacteria to humans. All RNA viruses have relatively high mutation rates, making their genomes highly variable. But in SARS and related viruses, one segment of the RNA genome known as the s2m RNA remains virtually unchanged.

"Because viral evolution has not been able to tamper with this sequence, it is clear that it must be of vital importance to the viruses that have it, but no one knows exactly what its function is," William Scott, associate professor of chemistry and biochemistry at UC Santa Cruz, said in a press release.

Scott's lab used the technique of x-ray crystallography to solve the structure of this RNA element with nearly atomic resolution, revealing where every one of the many thousands of atoms that make up the structure is situated. The results showed several unique and interesting features of the s2m RNA, including a distinctive fold that appears to be capable of binding to certain proteins involved in regulating protein synthesis in cells.

"The structure gives us strong hints about the function, because it forms a fold that has been implicated in binding a certain class of proteins," Scott said, "the structure itself also provides a starting point for designing antiviral drugs that might bind to this RNA and prevent it from doing whatever it is that is vital to the life cycle of the virus."

According to Scott, this research could lead to the development of antiviral drugs that would bind to the s2m RNA and prevent it from carrying out its function. Such drugs might be effective against a range of coronavirus. While the SARS virus is the most deadly of these, other coronaviruses are common causes of respiratory infections in humans and other animals.