A Tetrahymena thermophila G4-DNA Binding Protein with Dihydrolipoamide Dehydrogenase Activity

Abstract

<p>G4-DNA is a four-stranded structure that is formed by guanine-rich sequences. We report here the purification and characterization of a novel G4-DNA binding protein from <em>Tetrahymena thermophila</em>, designated TGP2. TGP2 was found to preferentially bind to G4-DNA oligonucleotides with adjacent single-stranded domains containing phosphorylated 5‘ ends and the sequence element, 5‘-ACTG-3‘. The amino acid sequence of TGP2 has high similarity to dihydrolipoamide dehydrogenase (DLDH) from a variety of species, and TGP2 was shown to have DLDH activity. Purified DLDH from porcine heart and bovine intestinal mucosa were shown to bind specifically to G4-DNA oligonucleotides. On the basis of these results we conclude that TGP2 is DLDH in <em>T. thermophila</em> and suggest that the G4-DNA binding capability of TGP2/DLDH may be biologically relevant.</p>