3-D structure of viral enzyme identified

WEST LAFAYETTE, Ind., Sept. 24 (UPI) -- U.S. biologists have determined the three-dimensional structure of an unusual viral enzyme that is required in the assembly of new viruses.

Purdue University scientists said the Paramecium bursaria chlorella virus infects a green alga called chlorella, transferring its DNA into host cells. Once inside the chlorella, the virus DNA makes an enzyme called glycosyltransferase, which is needed to produce structural proteins that are assembled to create the outer shells, or capsids, for new virus particles.

In contrast, many viruses commandeer the genes of host cells to make enzymes and proteins, said Ying Zhang, a postdoctoral researcher in the laboratory of Professor Michael Rossmann, who led the study.

The 3-D structure of the complete infectious virus had been determined earlier by the same researchers. Now they have found the structure of a specific type of glycosyltransferase and also its complex with a molecule called uridine-5-diphosphate-glucose, or UDP-glucose, along with positively charged manganese ions. The ions are critical because they coordinate the binding of the UDP-glucose to the enzyme, the researchers said.

The findings by Zhang, postdoctoral researcher Ye Xiang, Professor James Van Etten and Rossmann appear in the journal Structure.

Copyright 2007 by United Press International

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