The structure of icosahedral cytoplasmic deoxyriboviruses

It is proposed that the shell of icosahedral cytoplasmic deoxyriboviruses (ICDV) consists of a unit membrane modified by the apposition of an icosahedral lattice of morphological subunits. A second unit membrane appears to be closely associated with, or a part of, the inner nucleoprotein core of the virus. The two membranes are closely appressed at the periphery of mature intact virus particles. The presence of two unit membranes in mosquito iridescent virus particles is clearly illustrated, but can at present only be inferred in the case of two smaller insect ICDV's studied. It is emphasized that ICDV unit membranes are defined in this study on the basis of morphology alone.