The formation of empty shells upon pressure induced decapsidation of turnip yellow mosaic virus

The stability of turnip yellow mosaic virus (TYMV) was investigated under p ressure, using solution neutron small angle scattering. Dissociation produc ts were characterized by analytical ultracentrifugation and electron micros copy. At pH 6.0, TYMV remained unaffected by pressure, up to 260 Megapascal s (MPa), the highest pressure reached in these experiments. At pH 8.0, TYMV remained unaffected by pressure up to 160 MPa, but decapsidated irreversib ly above 200 MPa, giving rise to more and more empty shells upon increasing pressure. The organization of these empty shells was similar to that of th e capsid of native virions, apart from the presence of a hole corresponding to the loss of a group of 5-8 coat protein subunits, through which the RNA may have escaped. At variance with other small isometric viruses, the caps id of TYMV never dissociated under pressure into subunits or small aggregat es of subunits. This exceptional behavior of TYMV is probably due to the im portance of van der Waals contacts and hydrogen bonds in the stability of i ts capsid.