Chromatographic purification and immunological analysis of viral polypeptides of mouse mammary tumor virus

Abstract

The seven mouse mammary tumor virus (MMTV) structural polypeptides (GP52, GP36, P28, P23, P14, P12, and P10) were purified to apparent homogeneity. An improved and reproducible chromatographic method was used to obtain high yields of viral proteins from the same batch of isopycnically purified MMTV. The viral structural proteins were first extracted repeatedly with a high salt and high pH buffer in the presence of 1% Triton X-100. Loss of the minor viral proteins during column purification was minimized by first purifying the smaller molecular weight viral proteins (P14, P12 and P10) by oligo-d(T) column chromatography from the dissociated virions. The other four major viral polypeptides (GP52, GP36, P28 and P23) were then fractionated by affinity and ion-exchange columns. High titer polyclonal antibodies were produced against all of the seven structural proteins except P12 and P10. These antisera were monospecific and showed no cross-reactivity in radioimmunoassay towards other MMTV proteins. With minor modifications, this method has also been applied to purify other structural proteins from several different C-type retroviruses.