Unlike crystallographic methods, the EPR approach does not require crystallization of proteins. Thus, the EPR methods are widely applicable to studies of many important membrane proteins. Furthermore, the mechanistic aspects of the function of the membrane proteins are studied using the time-resolved EPR techniques. The influenza virus surface is coated with the HA protein which play a major role in the infection of host cells. The primary function of HA is to bring the viral and cellular membranes close together so that they can fuse.
Fusion allows the virus genome into the host cell where it replicates.
The protein conformational change and its interaction with the cellular membranes are, however, largely unknown. In our laboratory we express the membrane interacting domain of HA in E. coli. Spin labeling EPR and the crystallographic studies are pursued in parallel to elucidate the mechanism of HA-mediated membrane fusion. Thus, the effort also involves the understanding of the function of HIV gp160. Every living cell possesses the ability to respond to external signals.