"It's something no one would notice unless they take this component apart and look at how each small bit works," Macara said. "If you just asked how the intact Npap60 binds to its truck, it would always look the same, but by looking more closely you see this amazing switch mechanism. The way it works is very unusual, and is contrary to what scientists previously thought was the function of Npap60. Now we want to know if it helps the truck select different types of cargo."
How such selection might take place is the next step in the research by Macara and Mark E. Lindsay, a medical and doctoral degree student at the U.Va. School of Medicine who initiated and led the study.
Cargo entry into the nucleus is used for many different functions of living organisms," Macara said. "Proteins activate genes by entering the nucleus, and viruses must enter the nucleus in order to replicate. If we know how importins recognize nuclear entry codes, we may find out the mechanism for allowing or barring entry of viruses or proteins that switch on genes to cause disease."