Novel site-specific endonucleases F-TflI, F-TflIi and F-TflIV encoded by the bacteriophage T5
Akulenko, N.V.; Ivashina, T.V.; Shaloĭko, L.A.; Shliapnikov, M.G.; Ksenzenko, V.N.
Molekuliarnaia Biologiia 38(4): 632-641
2004
ISSN/ISBN: 0026-8984 PMID: 15456135 Document Number: 578552
Novel site-specific H-N-H endonucleases F-TflI, F-TflII and F-TflIV were identified. These endonucleases are encoded by open reading frames localized in the bacteriophage T5 tRNA gene region. The endonuclease F-TflIV was shown to introduce double-strand break into pseudo palindromic 17 bp DNA sequence yielding 1 bp extensions with 3'-overhangs. In contrast to F-TflIV, endonucleases F-TflI and F-TflII cleave only one strand of their asymmetric divergent DNA substrates. Each of these endonucleases introduces interruptions into only the particular strand (template or coding). Amino acid sequences of the endonucleases under study are highly homologous in the H-N-H motif regions and C-terminal sequences, forming putative catalytic domain. Endonuclease F-TflIV N-terminal region is homologous to the amino acid sequences representing H-T-H recognition domain found in LuxR family transcription regulators. Putative recognition NUMOD4 motif characteristic for a number of H-N-H endonucleases was shown to be also present in the endonuclease F-TflI and F-TflII N-terminal sequences. Two-domain structure was proposed for endonucleases F-TflI, F-TflII and F-TflIV with N-terminal recognition domain and C-terminal catalytic domain. A hypothesis of evolutionary origin of these endonucleases as a result of catalytic and recognition domains recombination was suggested.