Mayo Clinic researchers have shown that proteins on the surface of a cell twist a viral protein（病毒蛋白） into position, allowing the virus to start infection and cause disease, all in a movement as graceful¹ as a ballroom² dance. The findings appear in the current online issue of Nature Structural³ & Molecular⁴ Biology. A team led by Roberto Cattaneo, Ph.D., a Mayo molecular biologist, describes the crucial initial steps taken by attachment⁵ proteins of the measles⁶（麻疹） virus and related respiratory（呼吸的） viruses with their cellular⁷ partners, the receptors. To get there, the research team built "handles" at different locations on a viral attachment protein, allowing them to be grabbed by an artificial receptor to start the dance.

Visualize⁸ the measles virus. It is small and has an outer "envelope" with two proteins, one that interacts with a cellular receptor, its dance partner, and another that fuses the viral envelope with the cell membrane⁹, starting infection.

Measles virus, while long targeted for eradication¹⁰（消灭，根除） through vaccination¹¹, still affects 10 million people and kills some 197,000 each year around the world. A long-running question is how the cell entry process begins.

"It was known that the viral attachment proteins always come in pairs, and recently it became clear that two pairs form a quartet（四重奏） ," Dr. Cattaneo says. "Pairs initially¹² face each other, and we show here that the upper bodies separate when the dance begins. We suggest that they then engage a partner from the other pair of the quartet, while the legs are still dancing with those of the original partner."

As this dance continues, the cellular receptors weaken the layer of attachment proteins that protects a lower layer of fusion¹³ proteins. When enough quartets become twisted and unstable¹⁴, the top layer fails abruptly¹⁵. This failure causes unfolding of the proteins in the lower layer, and, in turn, fusion with the cellular membrane. The viral genome, now inside the cell, tells it to stop dividing and mandates¹⁶ the building of new viruses.

Dr. Cattaneo has studied viruses for three decades, primarily as tools for new medical discoveries. Viruses, he says, can be transformed into vectors（向量，带菌者） to treat disease. In 1999, he joined Mayo Clinic as a founding member of the Molecular Medicine Department. To date, two viral vectors developed at Mayo Clinic are in clinical trials to treat ovarian（卵巢的） cancer, glioma（胶质瘤） and myeloma（骨髓瘤） .