Researchers expressed the tobacco mosaic virus (TMV) 30K movement protein (MP) using a baculovirus expression system in insect cells (Spodoptera frugiperda). The MP gene was cloned into an Autographa californica nuclear polyhedrosis virus vector and introduced into insect cells, producing low levels of recombinant MP. The protein was detected as three species: two closely related forms of approximately 34 kilodaltons and a 32-kilodalton species. Analysis revealed the recombinant MP was not modified by N-linked glycosylation but was phosphorylated. The recombinant MP existed in both phosphorylated and unphosphorylated states, with the phosphorylated form migrating identically to plant-expressed MP on gel electrophoresis, confirming authenticity. The baculovirus expression system successfully produced authentic TMV MP with apparently correct post-translational modifications, providing larger quantities of protein than plant or bacterial expression systems for functional studies.

Key findings

• Tobacco mosaic virus movement protein was successfully expressed in insect cells using a baculovirus vector, producing three protein species (34K and 32K forms)
• The recombinant MP was phosphorylated but not N-glycosylated, as confirmed by tunicamycin treatment and concanavalin A lectin probing
• Phosphorylated recombinant MP showed identical electrophoretic mobility to plant-expressed MP, confirming authenticity of the protein
• The baculovirus expression system produced more accessible and larger quantities of MP compared to plant and bacterial sources, despite lower absolute expression levels