Summary auto-generated
This study examined how potato virus X (PVX) reacts with chemical reagents that modify lysine amino groups in proteins. The researcher treated intact PVX particles with four different reagents: pyridoxal-5-phosphate (PLP), 2,4,6-trinitrobenzenesulphonic acid (TNBS), methyl picolinimidate (MEP), and dansyl chloride. All reagents successfully reacted with lysine residues on the virus surface, as evidenced by changes in the virus's absorption spectrum, fluorescence properties, and electrophoretic mobility. Importantly, virus particles with one or two modified lysine residues per protein subunit retained 50-100% of their infectivity, while more extensive modification progressively reduced infectivity. The findings support the hypothesis that PVX-Q, an infective viral product formed when PVX encounters oxidized leaf phenols, contains chemically modified lysine residues. The results suggest that not all lysine residues are equally accessible, with evidence indicating one lysine per protein subunit is particularly reactive to chemical modification.
Key findings
- PVX lysine amino groups react with multiple protein-modifying reagents (PLP, TNBS, MEP, dansyl chloride), causing measurable changes in viral spectral properties and electrophoretic mobility
- Viral infectivity is retained when 1-2 lysine residues per protein subunit are modified (50-100% of original infectivity), but is progressively lost with more extensive modification
- The chemical charge of the modification matters: TNBS (acidic) and PLP (acidic) modifications were more compatible with infectivity than MEP (basic) modifications
- Evidence suggests one lysine residue per protein subunit is more reactive than others, possibly the trypsin-susceptible site previously identified
- These findings support the hypothesis that PVX-Q, an infective quinone-modified viral product, contains chemically modified lysine residues
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Abstract
Potato virus X reacted with reagents commonly used for protein amino groups, and some of its properties were changed. 2,4,6-trinitrobenzenesulphonic acid, pyridoxal-5-phosphate and methyl picolinimidate altered its absorption spectrum; the last two altered its fluorescence spectrum, and the first two altered its electrophoretic mobility. These reagents did not necessarily inactivate the virus; preparations judged to contain two modified amino groups per protein subunit retained 50 to 100% of their initial infectivity. This supports the previous conclusion that PVX-Q, an infective product of PVX and an oxidized leaf phenol, contains modified lysine -amino groups.