A SPECIFIC INTERACTION BETWEEN COAT PROTEIN AND HELPER COMPONENT CORRELATES WITH APHID TRANSMISSION OF A POTYVIRUS

Specific binding between the coat protein (CP) and the helper componen t (HC) of the tobacco vein mottling potyvirus (TVMV) was characterized using a protein blotting-overlay protocol. In this in vitro assay, HC interacted with either virions or CP monomers originating from the ap hid-transmissible TVMV-AT but not from the non-aphid-transmissible TVM V-NAT. There was a strong correlation between the aphid transmissibili ty of a series of TVMV variants having mutations in the DAG motif of t he CP and their ability to bind HC. Expression of TVMV CP derivatives in bacteria allowed a precise determination of the minimum domain medi ating HC binding. This domain is composed of seven amino acids, includ ing the DAG motif (DTVDAGK), located in the N-terminus of the TVMV CP at amino acid positions 2 to 8. (C) 1997 Academic Press.