The structure of an enzyme.

The structure of an enzyme essential for the operation of "molecular motors" that package DNA into the head segment of some viruses during their assembly has been discovered by researchers at The Catholic University of America, Washington, D.C. The enzyme (ATPase) provides energy to run the motor needed to insert DNA into the capsid, or head, of the T4 virus, which is called a bacteriophage because it infects bacteria. The same type of motor, however, also likely is present in other viruses, including that of human herpes.