A dodecapeptide (YQVTQSKVMSHR) exhibits antibacterial  effect and induces cell aggregation in Escherichia coli.
Antimicrobial peptides play an important role in the innate immune response and host defense mechanism. In the present study, we employed phage display technique to screen for inhibitors which may block the phosphoenolpyruvatedependent phosphotransferase system (PTS) pathway and hence retard cell growth. The recombinant histidine-containing phosphocarrier HPr protein was prepared as the target to screen for the tight binders from the phage-displayed random peptide library Ph.D.-12. The biopanning processes were performed and the binding capabilities of the selected phage were further estimated by enzyme-linked immunosorbent assay (ELISA). The single-stranded DNAs of the 20 selected phages were isolated, sequenced, and five corresponding peptides were synthesized. Only one of the five peptides, AP1 (YQVTQSK VMSHR) was found to inhibit the growth of Escherichia coli cells efficiently (IC₅₀~50 μM). Molecular modeling reveals that AP1 may block the EI-HPr interaction and phosphotransfer. Interestingly, AP1 was also found to induce cell aggregation in a concentration-dependent manner. Since glycogen accumulation has been attributed to biofilm formation, the effects of AP1 on the intracellular glycogen levels were measured. The results strongly indicate that the cell aggregation may be caused by the binding of peptide AP1 with HPr to block the interaction of dephosphorylated HPr with glycogen phosphorylase (GP). Because glycogen phosphorylase activity can be activated by HPr-GP interaction, the binding of AP1 to HPr would cause a decreasing rate of glycogen breakdown in M9 medium and accumulation of glycogen, which may lead to eventual cell aggregation. To the best of our knowledge, this is the first study to demonstrate that an inhibitor bound to a dephosphorylated HPr can decouple its regulatory function and induce cell aggregation.
Department of Life Science and Institute of Biotechnology, National Dong Hwa University, Taiwan 974, Republic of China.
Kuo-Chih
KC
Lin
Chih-Yuan
CY
Chen
Chih-Wei
CW
Chang
Kuo-Jien
KJ
Huang
Shih-Pin
SP
Lin
Shih-Hung
SH
Lin
Ding-Kwo
DK
Chang
Meei-Ru
MR
Lin
David
D
Shiuan
D000900:Anti-Bacterial Agents / Q000378:metabolism*; D001422:Bacterial Adhesion / Q000187:drug effects*; D001426:Bacterial Proteins / Q000378:metabolism; D004926:Escherichia coli / Q000187:drug effects* / Q000254:growth & development / Q000502:physiology; D020128:Inhibitory Concentration 50; D008958:Models, Molecular; D009842:Oligopeptides / Q000378:metabolism*; D019151:Peptide Library; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000378:metabolism; D011485:Protein Binding
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D009842:Oligopeptides; D019151:Peptide Library; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; C030182:phosphocarrier protein HPr