Isolation and comparative biochemical properties of the major internal polypeptides of equine infectious anemia virus

Abstract

Procedures for the large-scale production of equine infectious anemia virus (EIAV) and for the isolation of the 4 major non-glycosylated virion proteins, designated p26, p15, p11, and p9, were described. Comparisons of the purified proteins by peptide mapping procedures and by enzyme-linked immunosorbent assays demonstrated the unrelatedness of the 4 proteins. The characteristic properties of each purified protein were examined by determining isoelectric points [pI] and amino acid compositions. EIAV p26 and p9 focus at pI values of 6.2 and 5.0, respectively, and these proteins contain no unusual amino acids. EIAV p15 reproducibly displayed a heterogeneous isoelectric focusing pattern, with major pI values ranging from 5.7-8.3. This charge variation evidently correlated with different levels of phosphorylated serine or threonine or both, which could be detected by an amino acid analysis of purified p15. EIAV p11 apparently focused at a pI of > 10, reflecting its high content of basic amino acids. Localization experiments indicated that all 4 nonglycosylated proteins constitute the internal components of the virus, with all of the virion p11 closely associated with the viral RNA genome. EIAV, a lentivirus, apparently contains structural polypeptides which are analogous to the structural polypeptides described previously in prototype C oncoviruses.