Abstract: Trichoplusia ni granulovirus (TnGV) enhancin can enhance the infectivity of virus in several insect hosts. It has a conserved zinc-binding domain commonly found in metalloproteases, HELGH, which is also present in enhancin proteins from other baculoviruses. In the current work, each of the five amino acids in the domain was mutated to be two different amino acids, and the total 10 mutant enhancin genes were used to construct recombinant AcMNPV. The expression of enhancin proteins was observed in virus-infected cells. Peritrophic membrane (PM) assay indicated all but one mutant lost the ability to degrade the insect intestinal mucin in PM. The only exception was the mutant in which glycine in position 4 was mutated to alanine. The results showed that the zinc-binding domain in enhancin was essential for the activity of the protein, and also suggest that baculovirus enhancin is a metalloprotease.

Key words: Baculovirus, enhancin, metalloprotease, peritrophic membrane, site-directed mutagenesis