The spatial arrangement of the wild-type and mutant tobacco mosaic virus coat proteins assessed by tritium planigraphy

Mutant ts21-66 of the tobacco mosaic virus (TMV) differs from the wild-type TMV-UI by two mutations (Ile21 --> Thr and Asp66 --> Gly) in the coat prot ein (CP) gene and in symptoms produced in infected N ' plants. The CP struc ture in TMV-U1 and ts21-66 virions was probed by tritium planigraphy. Compa red with the wild-type CP, labeling of the N-terminal region of mutant CP w as half as high and suggested its greater shielding. The role of this CP re gion in virus interactions with the N ' resistance system is discussed.