Virus Enzymes and Virus Templates

Abstract

It appears that the viruses proper do not possess an integrated respiratory system, i.e. they have no autonomous metabolism. The evidence for this statement is provided by an analysis of the published data on the quantity and the structural features of the protein moiety of animal, plant and bacterial viruses consisting of nucleoprotein only. The lack of an energy-providing enzyme system differentiates the viruses proper from the parasitic bacteria. On this criterion the rickettsiae resemble the bacteria more closely than viruses proper. There is no conclusive evidence in the literature that a type of enzyme present in the host cell is an intrinsic component of a true virus. So far, only the influenza virus neuraminidase catalyzing the release of the terminal neuraminic acid from its mucoprotein substrate has been shown to be an integral part of the virus particle. From recent data on bacterial viruses and on tobacco mosaic virus it seems that virus nucleic acid is the carrier of genetic determinants and that this material is the main, if not the only, virus component responsible for the diversion of the host cell metabolism from the synthesis of host protein and host nucleic acid to the synthesis of the corresponding virus materials. The degree of diversion from the manufacture of host cell macromolecules to that of virus macromolecules of similar type will be governed by the relative concentrations of host and virus genetic coenzymes and by their relative affinities for the common host apoenzymes. The smaller viruses, consisting of nucleic acid and a protective protein coat, must represent the lowest level of living matter because it would be difficult, if not impossible, to conceive of a simpler equipment of any self-replicating unit than the template embodying the specific information about its individuality.