Two-dimensional gel analyses of the 24-kDa cap binding protein from poliovirus-infected and uninfected HeLa cells.

The 24-kDa cap binding protein (CBP) from uninfected, mock-infected and poliovirus-infected HeLa cell extracts was isolated by m7GTP affinity chromatography and examined by isoelectric focusing followed by SDS-PAGE. Two major species (pI 6.7 and 7.1) and two minor species (pI 6.5 and 6.8) were found in all cases. Preparations from postribosomal supernate (S200) and the supernate from 0.5 M KCl washed ribosomes (RSW) also demonstrated these same four species. We conclude that there are no detectable differences between ribosome-associated and soluble 24-kDa CBP and that the 24-kDa CBP is not detectably altered by poliovirus infection. We also report the presence of a previously undescribed 16-kDa polypeptide(s) doublet that copurifies with the 24-kDa CBP from uninfected, mock-infected and poliovirus-infected HeLa cells.