During the process of bacterial DNA replication, DNA Polymerase, which catalyze the synthesis of DNA, plays an indispensable role. In order to keep DNA Polymerase III sliding along, a protein complex namely β-clamp forms a ring-like structure around DNA, serving as a processivity -promoting factor. Due to the critical function of β-clamp in the replication of bacteria and the formation of tumors, various β-clamp inhibitors have been investigated to a great extent for antibacterial studies.
Recently, a research team led by Prof. ZHANG Kaiming from University of Science and Technology of China (USTC) of the Chinese Academy of Sciences found the Gp168 protein of bacteriophage Twort inhibited β-clamp function by occupying the DNA sliding channel. The study was published in Nucleic Acids Research .
The research team reported a cryo-EM structure of the clamp-Gp168 complex at 3.2-˚A resolution. Researchers revealed that the Gp168 dimer occupied the DNA sliding channel of β-clamp and blocked its loading onto DNA.
In previous studies, most of the published β-clamp inhibitors and binding proteins engaged the β-clamp via hydrophobic protein-binding pocket. Meanwhile, since Gp168 could form complex with the β-clamp of Staphylococcus aureus and Bacillus subtilis, it is potentially a cross-species β-clamp inhibitor.
To understand the formation of the Gp168-clamp complex, the researchers identified that Gp168 existed as a hexameric complex in solution. The pulled-down experiment involving Gp168 and the β-clamp of Staphylococcus aureus showed that Gp168 could form a stable complex with the β-clamp of Staphylococcus aureus. The researchers subsequently performed the cryo-EM single-particle analysis mentioned above to further understand the detailed structure of the Gp168-clamp complex.
Based on the results, they concluded that Gp168 likely represented a new class of proteins with other members yet to be discovered.
The study not only reveals an alternative mechanism for bacteriophages to inhibit β-clamp but also provides inspiration for the development of new antimicrobial reagents.
Nucleic Acids Research
Bacteriophage Twort protein Gp168 is a β-clamp inhibitor by occupying the DNA sliding channel
6-Oct-2021