Figure 5.

Modulation of M2-PK by E7 in vitro. (Upper) Extracts from M/1 cells were incubated with GST (90 ng/μl) or GST-HPV16E7 (90 ng/μl) for 1 hr at 4°C and subjected to gel filtration. Activity of M2-PK was measured in all fractions in the presence of 2 mM PEP. On addition of GST-HPV16E7, the proportion of tetrameric M2PK was reduced from 63% to 54%, and the proportion of dimeric enzyme increased from 37% to 46%. For calibration of the column, the maximal activities of GAPDH, lactate dehydrogenase (LDH), and enolase (EN) were determined in the individual fractions. (Lower) The distribution of M2-PK and GST-16E7 in the fractions was monitored by direct immunoblotting using antibodies against M2-PK and GST, respectively.