Polypeptide components of rice dwarf virus.

Abstract

Polyacrylamide gel electrophoresis of the solubilized protein of rice dwarf virus (RDV), purified from RDV-infected rice plants, showed the virus to be composed of seven structural polypeptides. The molecular weights of these were calculated to be 193,000; 152,000; 131,000; 110,000; 62,000; 46,000 and 45,000 daltons.These were designated I, II, III, IV, V, VI, and VII respectively. Chymotrypsin-treatment of the virus was not effective for removing the outer components of capsid, whereas centrifugation of the virus through preformed cesium chloride gradients separated the preparation into four zones, top (T), upper-middle(M1), lower-middle (M2), and bottom (B), the buoyant densities of these being 1.26, 1.39-1.42, 1.43, and 1.46g/ml respectively. Recentrifugation of M1 through the cesium chloride gradients yielded three zones, M1, M2, and B, indicating that the latter two resulted from M1 by the shearing effect of cesium chloride centrifugation.Electron microscopy and SDSpolyacrylamide gel electrophoresis of B showed complete loss of II and IV, and a marked decrease of VI and VII, indicating that VI and VII compose the outer capsomeres and II and IV are the amorphous polypeptides that surround the outer capsomeres. The inner core was found to contain I, III, and V, among these V seemed to be the internal protein associated with nucleic acid because this was readily released from virions by freeze-thawing together with nucleic acid.

Location of Structural Proteins in Particles of Rice Gall Dwarf Virus

“…3a, 4a) in RGDV, 131K and 46K + 45K in RDV (Nakata et al, 1978) and 118K and 36K + 35K in WTV (Reddy & Macleod, 1976). It is interesting that the larger proteins are located in the cores and the smaller proteins are found in the capsid (Table 1 ; Nakata et al, 1978 ;Reddy & Macleod, 1976). The 45K protein of RGDV did not separate into two bands in our experiment, but the corresponding bands of RDV and WTV separated into two (46K and 45K in RDV,and 36K and 35K in WTV).…”

“…Immunological detection of polypeptides on nitrocellulose sheets using fluorescein-conjugated sheep anti-rabbit IgG (Cappel Laboratories) was performed by the method of Towbin et al (1979) modified by Matsuoka & Asahi (1983). Reddy & Macleod (1976) and Nakata et al (1978) separated the outer capsid from the core of WTV and RDV, respectively, by centrifuging particles in CsC1 density gradients; this method was applied to RGDV particles. The pH of the buffer has been reported to have a marked effect on CsC1 equilibrium sedimentation of bluetongue virus (Verwoerd et al, 1972) and WTV (Reddy & Macleod, 1976).…”

“…The Phytoreoviruses such as wound tumour virus (WTV) (Reddy & Macleod, 1976) and rice dwarf virus (RDV) (Nakata et al, 1978) have six or seven similar-sized protein components that differ in size from the six particle proteins of maize rough dwarf virus (Boccardo & Milne, 1975) and the three particle proteins of core preparations of Fiji disease virus (Van der Lubbe et al, 1979), both of which are Fijiviruses. We have examined the number and molecular weights of the protein components of RGDV to see if these are similar to those of WTV and RDV.…”

Sequence analysis and product assignment of segment 7 of the rice dwarf virus genome

“…These proteins are encoded by the viral genomic RNAs and include those with polymerase activity (Kodama & Suzuki, 1973). The protein product of segment 7 was previously predicted to be the 60 K core protein of RDV (Nakata et al, 1978) because of its size (about 1600 bp). Here, we report on the results of sequence analysis~and expression in vitro of segment 7.…”

“…Rice dwarf virus (RDV) (Phytoreovirus subgroup) consists of 12 genome segments of dsRNA (Fujii-Kawata et al, 1970;Kimura et al, 1987) and seven structural proteins (Nakata et al, 1978;Kimura et al, 1987). These proteins are encoded by the viral genomic RNAs and include those with polymerase activity (Kodama & Suzuki, 1973).…”