Chemical crosslinking of major structural proteins within type D retroviruses

The nearest neighbor relationships of major structural proteins within type D retroviruses (SMRV, MPMV, PMFV) were investigated by crosslinking with the cleavable bifunctional reagent dimethyl dithiobispropionimidate (DTBPI) or by use of 2-iminothiolane (methyl mercaptobutyrimidate, MBI) and subsequent oxidation by hydrogen peroxide. The crosslinked complexes of proteins were analyzed by two-dimensional diagonal polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. In intact virions both crosslinking reagents induced the formation of covalently linked complexes of the internal structural proteins as well as complexes containing the envelope glycoproteins. The following complexes were found for each virus: SMRV: (pp20)2; (p35)2,4,6; (pp20-gp68); MPMV: (p10)2,4,6; (p25)2,4; (p10-p25); (gp20-gp68); (p45-gp68); PMFV: (p10)2; (p25)2; (p10-p25); (p45-gp68). In control experiments without crosslinking reagents no covalently linked complexes were detected.