Effect of Protein Cross-linking Reagents and Sodium Dodecyl Sulfate on Southern Bean Mosaic Virus

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Abstract
Sodium dodecyl sulfate (SDS) sensitivity of the native and divalent cation-free virions of southern bean mosaic virus (SBMV) was examined under the various conditions. In the absence of SDS (25.degree. C, 1 h), native virions sedimented at 115S between pH 2.5 and 9.5; at pH 10.0-10.5, SBMV was converted progressively into a 60-65S entity; but it was degraded into a 35-40S nucleoproteinaceous products at pH 11.0. In the presence of 0.1% SDS, SBMV dissociated readily at pH 2.5-3.0 or pH 10.5-11.0; an increasing proportion of the virions were rendered SDS-sensitive at pH 9.5-10.0, but they were stable in the presence of SDS within the pH range of 3.5-9.0. Virions were dissociated with 2% SDS at pH 5.5 if exposed at 60-70.degree. C for 10 min, but remained structurally stable in 0.5 M NaCl plus SDS. Divalent cation-free SBMV in the swollen form (100 S) at pH 7.5 or in the compact conformation (115S) at pH 5.5 was sensitive to SDS. When treated with the protein cross-linking reagents, namely formaldehyde or dimethyl adipimidate, swollen SBMV at pH 7.5 was transformed into a sharply sedimenting 105-107S form, but remained sensitive to SDS. With additional stabilization of the viral capsid by reducing the pH to 5.5, such virions sedimented uniformly at 115S and also became resistant to SDS. These results are discussed relative to the available information on SBMV-stabilizing interactions.