Self-association and mapping of interaction domains of helper component-proteinase of potato A potyvirus

Potyviral helper component-proteinase (HC-Pro) is a multifunctional protein involved in aphid transmission, long-distance movement, polyprotein proces sing, genome amplification and symptom expression. It has been proposed tha t the active form of HC-Pro is a dimer and that coat protein (CP)-HC-Pro in teraction is required for aphid transmission. To test these proposed intera ctions between CP and HC-Pro of potato A potyvirus (PVA), the yeast two-hyb rid system was used. HC-Pro was shown to interact with itself in vivo in ye ast cells, as did CP, Taken together with previous observations, we conclud e that the functional HC-Pro is a homodimer. Deletion analysis showed that a 24 aa domain in the N-terminal half and the C-terminal proteinase part of HC-Pro were required for the interaction between HC-Pro molecules. No inte ractions were found between HC-Pro and CP using the genes of aphid-transmis sible as well as aphid non-transmissible strains of PVA.