We have obtained evidence that poliovirus and other picornavirus particles are specifically modified by having myristic acid covalently bound to a capsid protein. The electron density map of poliovirus confirms the position of the myristate molecule and defines its location in the virus particle. Analogies with other myristylated proteins suggest that the myristate moiety in picornaviruses may be involved in capsid assembly or in the entry of virus into cells.

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SUMMARYNodamura virus, a small non-enveloped RNA virus, contains two species of RNA sedimenting at 22S (RNA-0 and I5S (RNA-2), a single major polypeptide of mol. wt. 4o x Io 3 and two minor polypeptides, of tool. wt. 38 and 43 x io ~. Evidence is presented that the two RNA species are in the same particle. Although extraction of the virus with SDS-phenol yields the two species of RNA as separate entities, gentle treatment of the virus with guanidine and low concentrations of SDS releases the RNA as a z7S component which contains both RNA-I and RNA-2 together with a trace of protein. It seems likely that the two RNA species replicate separately because double stranded molecules corresponding to the single stranded RNA-1 and RNA-2 molecules were present in BHK cells infected with the virus.

SUMMARYTrypsin (o.Img./ml.) reduced the infectivity of vesicular stomatitis virus by 5 log. within 5 miD. and destroyed immunizing activity. It also destroyed the complement-fixing activity against antiserum to the virus but the activity against antiserum to host cells was unaffected. The external spike-like projections of the virus were removed without affecting the remainder of the surface structure. Trypsin removed radioactivity from virus labelled with [l~C]amino acids, but not from virus labelled with 3~p.Phospholipase reduced the infectivity to a much smaller extent than trypsin and the immunizing activity was apparently unaffected. After treatment with phospholipase, complement-fixing activity against antiserum to virus was also unaffected but the complement-fixing activity against antiserum to host cells was greatly reduced. Electron microscopy showed that the spike structure of the virus was unaffected by phospholipase C but the remainder of the surface was digested. The enzyme removed more than 5o% of radioactivity from virus labelled with asp in the phospholipid component. The results showed that the spike-like structure of the virus responsible for producing neutralizing antibodies is composed entirely of virus protein and the phospholipid component derived from the cells is located in the regions between the spikes. The spikes may be attached directly to the internal helical structure of the virus.

Vesicular stomatitis virus contains single-stranded ribonucleic acid of molecular weight 3.6 X 106 and three major proteins with molecular weights of 75 x 103, 57 x 108, and 32.5 X 103. The proteins have been shown to be subunits of the surface projections, ribonucleoprotein, and matrix protein, respectively. From these values and from estimates of the proportions of the individual proteins, it has been calculated that the virus has approximately 500 surface projections, 1,100 protein units on the ribonucleoprotein strand, and 1,600 matrix protein units. Possible models of the virus are proposed in which the proteins are interrelated.