FROM A PORE TO A CAVITY

Abstract

THE BACTERIAL PORE-FORMing protein ?-hemolysin has been engineered to bind two different cyclodextrins at different sites, forming a cavity. Organic molecules pulled into the space are confined for up to hundreds of milliseconds { Science , 291 , 636(2001)}. ?-Hemolysin, whose shape allows it to poke holes in membranes, is the toxin secreted by Staphylococcus aureus . The pore it forms is an ion channel, whose properties can be deduced from electrical measurements. For years, Hagan Bayley, a professor of medical biochemistry and genetics at Texas A&M University's Health Science Center, has been modifying this protein and endowing it with various properties. With coworkers Li-Qun Gu and Stephen Cheley, Bayley has now engineered ?-hemolysin so that two chemically different cyclodextrins bind spontaneously in an ordered way. Both bind tightly, staying in place for seconds, Bayley says. And while bound, both are still able to take part in the host-guest chemistry that they usually do in solution. Bayley's pre...