Isoelectric Focusing Studies of Mengo Virus Variants, their Protein Structure Units and Constituent Polypeptides

Abstract

Virions of 3 plaque variants (L-, M- and S-) of Mengo virus, which assume a bimodal distribution when subjected to isoelectric focusing in sucrose-stabilized pH gradients containing 0.5% Brij 35, banded in a single peak (at pH 8.1-8.4) when focused under the same conditions in gradients supplemented with 6 M-ethylene glycol. An examination of M-Mengo virions, isoelectric at pH 4.7 and 8.4 in sucrose-stabilized gradients, showed that the 2 populations were indistinguishable on the basis of specific infectivity, polypeptide composition and sedimentation characteristics, but differed in their ability to agglutinate human erythrocytes. When pH-inactivated virions were subjected to isoelectric focusing, 3 well defined peaks were produced, 1 of which corresponded to the well characterized 13.4S subunit of Mengo virus, and the other 2, on the basis of compositional analysis, to virions that lost some of their 13.4S structure units. No difference in electrophoretic behavior was found among the 13.4S subunits isolated from the 3 Mengo variants; all 3 were isoelectric at pH 5.85-6.00. Analysis, by isoelectric focusing, of the 4 structural polypeptides (.alpha., .beta., .gamma., .delta.) isolated from L-, M- and S-Mengo failed to reveal any significant differences among the 3 variants.