Apparent allosterism by avian myeloblastosis virus reverse transcriptase and E. coli DNA polymerase I.

A recent report (1) presented evidence for allosterism in reverse transcription by Mason-Pfizer monkey virus reverse transcriptase and by E. coli DNA polymerase I. Our experiments also demonstrate these apparent cooperative effects when synthesis is catalyzed by either avian myeloblastosis virus DNA polymerase, feline sarcoma virus DNA polymerase, or E. coli DNA polymerase I (large fragment). We show that the apparent cooperativity depends on the use of oligo(dT)12-18 as primer. However, if the polymerase reaction products are isolated chromatographically, then the polymerases obey classical Michaelis-Menten kinetics with respect to substrate and enzyme concentrations. These results suggest that the cooperative effects are an acid precipitation artifact. The results are also consistent with the enzyme operating by a distributive mechanism with the oligo(dT)12-18 primer.