The thermal stability of capsids of the bacteriophage MS2, lacking genomic RNA, has been investigated using electron microscopy. Coat protein mutants with amino acid substitutions at residues involved in making contacts at both inter-molecular interfaces and within the coat protein subunit are also capable of forming ‘empty’ capsids of the same size and symmetry as the wild-type protein. Mutations have been characterised which are neutral, deleterious or advantageous in terms of thermal stability. In some cases, the results can be rationalised by reference to the recently refined X-ray crystal structure of the wild-type particle.
