Replication complexes that contained either murine leukemia virus reverse transcriptase (MLV RT) or a variant reverse transcriptase without a ribonuclease (RNase) H domain (ΔRH MLV RT ) were visualized by enzymatic footprinting. Wild-type MLV RT protected template nucleotides +6 to -27, and primer nucleotides -1 to -26 of primers that had first been extended by one or four nucleotides. Although it catalyzed DNA synthesis, ARH MLV RT stably bound template-primer only under conditions of reduced ionic strength and protected the duplex portion only as far as position -15. Despite altered hydrolysis profiles, both enzymes covered primarily the template-primer duplex, contradicting recent predictions based on the structure of rat DNA polymerase β.
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