Jw. Rausch et al., INVOLVEMENT OF C-TERMINAL STRUCTURAL ELEMENTS OF EQUINE INFECTIOUS-ANEMIA VIRUS REVERSE-TRANSCRIPTASE IN DNA-POLYMERASE AND RIBONUCLEASE-H ACTIVITIES, Journal of Molecular Biology, 257(3), 1996, pp. 500-511
In order to investigate the modes of DNA synthesis supported by the 66
and 51 kDa subunits of equine infectious anemia virus reverse transcr
iptase (EIAV RT), recombinant p66 polypeptides containing a modified r
ibonuclease H (RNase H) domain were purified and evaluated. Defined he
teropolymeric template-primer combinations and high-resolution gel ele
ctrophoresis provided a qualitative evaluation of DNA polymerase and R
Nase H activities, while DNase I footprinting revealed features of rep
lication complexes containing the truncated enzymes. Removal of alpha-
helix E ' and the conserved beta 5 '-alpha E ' ''His-loop'' in p66 Del
ta 20 RT uncouples the RNase H activities, alters affinity for templat
e-primer and dictates how the replicating enzyme responds to secondary
structure on both DNA and RNA templates. Despite these alterations, D
Nase I footprinting shows no major difference in the overall structure
of DNA-directed DNA synthesis complexes. In contrast, removing 47 C-t
erminal residues, which includes alpha-helix D ', beta-strand 5 ' and
alpha-helix E ', yields an enzyme with distributive DNA polymerase pro
perties closely resembling the purified p51 subunit. (C) 1996 Academic
Press Limited