X ‐ray structure of a superinfection exclusion lipoprotein from phage TP ‐ J 34 and identification of the tape measure protein as its target

Summary Lipoproteins of temperate phage are a broad family of membrane proteins encoded in the lysogeny module of temperate phages. Expression of the ltp TP ‐ J 34 gene of temperate S treptococcus thermophilus phage TP ‐ J 34 interferes with phage infection at the stage of triggering DNA release and injection into the cell. Here, we report the first structure of a superinfection exclusion protein. We have expressed and determined the X ‐ray structure of Ltp TP ‐ J 34 . The soluble domain of Ltp TP ‐ J 34 is composed of a tandem of three‐helix helix–turn–helix ( HTH ) domains exhibiting a highly negatively charged surface. By isolating mutants of lactococcal phage P 008wt with reduced sensitivities to Ltp TP ‐J34 and by genome sequencing of such mutants we obtained evidence supporting the notion that Ltp TP ‐ J 34 targets the phage's tape measure protein ( TMP ) and blocks its insertion into the cytoplasmic membrane.