NP is one of only 11 proteins that are encoded by the influenza A genome. One of its main functions is structural. Once the virus has hijacked a host cell, and converted it into a virus-replicating factory, the NPs come together in small rings as building blocks. Many NP rings stack one atop the other in a slightly off-registered fashion, forming long helical-shaped columns. The virus's RNA genome is twisted around this column and shipped out to infect other cells.
"NP has about 500 amino acids and the tail loop contains about 30 of those," Tao said. "We found that a mutation in only one residue out of 30 was enough to prevent the NPs from coming together to form the building blocks for the columns, and without these columns the virus cannot make copies and infect other cells."
Tao said the research also provides clues about NP's role in signaling a cell to begin making copies of the viral genome, and Tao's group is continuing its work with co-author Robert Krug at the University of Texas at Austin to explore the protein's regulatory functions.