Removal of the N-terminal part of alfalfa mosaic virus coat protein interferes with the specific binding to RNA 1 and genome activation.

Trypsinized coat protein of alfalfa mosaic virus lacking 25 amino acids at its N terminus still has the capability to form complexes with RNA which are detectable by sedimentation in sucrose gradients. However, it does not protect specific sites on the RNA against degradation by ribonuclease, as the native coat protein does (D. Zuidema, M. F. A. Bierhuizen, B. J. C. Cornelissen, J. F. Bol, and E. M. J. Jaspars (1983) Virology 125, 361-369.). The trypsinized coat protein has lost the capacity of the native coat protein to make the genome RNAs of alfalfa mosaic virus infectious or to interfere with the infectivity brought about by the native coat protein. These findings suggest that genome activation occurs via binding of the N-terminal part of the coat protein to specific sites on the RNAs.