title: A reverse transcriptase-related protein mediates phage resistance and polymerizes untemplated DNA in vitro.
abstract: Reverse transcriptases (RTs) are RNA-dependent DNA polymerases that usually function in the replication of selfish DNAs such as retrotransposons and retroviruses. Here, we have biochemically characterized a RT-related protein, AbiK, which is required for abortive phage infection in the Gram-positive bacterium Lactococcus lactis. In vitro, AbiK does not exhibit the properties expected for an RT, but polymerizes long DNAs of 'random' sequence, analogous to a terminal transferase. Moreover, the polymerized DNAs appear to be covalently attached to the AbiK protein, presumably because an amino acid serves as a primer. Mutagenesis experiments indicate that the polymerase activity resides in the RT motifs and is essential for phage resistance in vivo. These results establish a novel biochemical property and a non-replicative biological role for a polymerase.
authors.affiliation: Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Chen
authors.initials: C
authors.lastname: Wang
authors.forename: Manuela
authors.initials: M
authors.lastname: Villion
authors.forename: Cameron
authors.initials: C
authors.lastname: Semper
authors.forename: Colin
authors.initials: C
authors.lastname: Coros
authors.forename: Sylvain
authors.initials: S
authors.lastname: Moineau
authors.forename: Steven
authors.initials: S
authors.lastname: Zimmerly
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001435:Bacteriophages / Q000502:physiology*; D004247:DNA / Q000096:biosynthesis / Q000737:chemistry; D004259:DNA-Directed DNA Polymerase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D013294:Lactococcus lactis / Q000821:virology; D008969:Molecular Sequence Data; D009154:Mutation; D017434:Protein Structure, Tertiary; D012194:RNA-Directed DNA Polymerase / Q000737:chemistry; D017386:Sequence Homology, Amino Acid
chemical_list: C106520:AbiK protein, Lactococcus lactis; D001426:Bacterial Proteins; D004247:DNA; D012194:RNA-Directed DNA Polymerase; D004259:DNA-Directed DNA Polymerase