Expression of CaMV ORF IV in Escherichia coli

Characterization of different electrophoretic forms of cauliflower mosaic virus virions (strain Cabb-S)

The electrophoretic forms of purified cauliflower mosaic virus (CaMV), strain Cabb-S, were examined by electrophoresis on agarose gels. Three populations of viral particles were identified: a faster migrating component (the form F) and two slower migrating components (the forms S and S'). When the different forms of virions, after excision from gels, were subjected to analysis in SDS-polyacrylamide gel, the fast component consisted of the 37 and 42 kDa coat proteins whereas the slow components contained mainly the 39 kDa coat protein. However, there was no difference among the nucleic acids associated within the three forms. The biological significance of the different components is discussed.

Processing of the minor capsid protein of the cauliflower mosaic virus requires a cysteine proteinase

The major capsid protein of the cauliflower mosaic virus (CaMV) is processed in vivo. The viral aspartic proteinase that catalyses this maturation has been characterized previously and is coded by the CaMV gene V. This virus has a second capsid protein, a minor component, encoded by gene III. This protein, P3, is also processed at its C-terminus in vivo. To determine whether P3 is matured by the CaMV proteinase P5, we expressed, in Saccharomyces cerevisiae, P3, P5 and a fusion protein P7-P4, containing potential sites of cleavage. P5 was found to be involved in maturation of P7-P4 but did not cleave P3. The latter result was confirmed by experiments carried out with an in vitro translation system (the reticulocyte lysate) and with preparations of replication complexes purified from infected plants. Moreover, [N-(L-3-trans-carboxyoxiran-2-carbonyl)-L-leu cyl]-amido(4-guanido)butane, a specific inhibitor of cysteine proteinases, inhibited the maturation of P3, suggesting that the two CaMV capsid proteins are not processed by the same proteolytic event.

A 37 kilodalton protein kinase associated with cauliflower mosaic virus

The cauliflower mosaic virus (CaMV) particle-associated protein kinase (PK) was shown to be a 37 kD protein in activity gels. In vitro experimental data concerning virus dephosphorylation or hyperphosphorylation suggested a possible regulation mechanism of this PK. The origin of the enzyme, either virus-encoded or from a host cell, is discussed.