J. Biol. Chem., Vol. 265, Issue 15, 8490-8496, May, 1990
Reverse transcriptase from Escherichia coli exists as a complex with msDNA and is able to synthesize double-stranded DNA
BC Lampson, M Viswanathan, M Inouye and S Inouye
Department of Biochemistry, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Piscataway 08854- 5635.
Reverse transcriptase required for the synthesis of msDNA.Ec67 in an
Escherichia coli strain was purified as a large molecular weight complex
with msDNA. The complex sedimented in a glycerol gradient at an s value
greater than 19. The predominant protein species co-purifying with reverse
transcriptase activity in the complex had a molecular weight estimated at
65,000 which is close to the expected size of 67,227 for the Ec67-reverse
transcriptase. In addition, the large complex also contained msDNA.Ec67.
The purified complex was able to synthesize cDNA using 5 S rRNA as a
template (annealed to a synthetic DNA primer), and a double-stranded DNA
using a synthetic DNA template (annealed to a synthetic DNA primer). When
msDNA.Ec67 was used as a natural template:primer, the purified complex
produced two major products: a 103-base single-stranded DNA by extending
the 3' end of msDNA using msdRNA as a template, and a 60-base
double-stranded DNA product resulting from the converse reaction in which
the 3' end of msdRNA is extended using msDNA as a template. The results
suggest that bacterial reverse transcriptase is capable of producing
single-stranded cDNA and possibly double-stranded DNA as well. Possible
implications of these findings on the biology of the msDNA-retron system
are discussed.