Since lytic phages excel at setting host processes to their hand and killing their hosts, they could provide new insights in combatting bacterial pathogens. A significant amount of the host reorganization is directed through interaction of phage early proteins with host proteins. However, the function of these phage proteins is largely unknown. Moreover, most of them have little to no sequence homology with known proteins, making functional predictions difficult.
The early phage protein studied here is gp14 from Pseudomonas aeruginosa phage LUZ7. This protein was previously shown to be toxic when expressed in P. aeruginosa, leading to filamentous growth of the cell [1]. Based on in silico predictions, we tested this protein for DNA binding activity in various Electrophoretic Mobility Shift Assays (EMSAs). The results show sequence independent binding to both dsDNA and ssDNA, with a much higher affinity for ssDNA. Using X-ray data, a model of gp14 was built. The model shows the protein occurs as a homodimer with features of an OB-fold. This is a fold commonly found in ssDNA binding proteins and supports the ssDNA binding character of the protein.
Comparison of Pseudomonas phage LUZ7 to coliphage N4 might indicate that this ssDNA binding phage protein is a functional analogue of N4 gp2, a protein recently elucidated in E. coli. Interestingly, both proteins have no sequence similarity whatsoever, but their biological role in shifting transcription from early to middle phase might be conserved.


REFERENCES
[1] Wagemans, J., Blasdel, B. G., Van den Bossche, A., Uytterhoeven, B., De Smet, J., Paeshuyse, J., Cenens, W., Aertsen, A., Uetz, P., Delattre, A., Ceyssens, P., Lavigne, R. (2014). Functional elucidation of antibacterial phage ORFans targeting Pseudomonas aeruginosa. Cellular Micrbiol. 16: 1822-1835