7evp
Cryo-EM structure of the Gp168-beta-clamp complex
Structural highlights
FunctionDPO3B_STAAU Confers DNA tethering and processivity to DNA polymerases and other proteins. Acts as a clamp, forming a ring around DNA (a reaction catalyzed by the clamp-loading complex) which diffuses in an ATP-independent manner freely and bidirectionally along dsDNA. Initially characterized for its ability to contact the catalytic subunit of DNA polymerase III (Pol III), a complex, multichain enzyme responsible for most of the replicative synthesis in bacteria; Pol III exhibits 3'-5' exonuclease proofreading activity. The beta chain is required for initiation of replication as well as for processivity of DNA replication.[UniProtKB:P0A988] Publication Abstract from PubMedBacterial chromosome replication is mainly catalyzed by DNA polymerase III, whose beta subunits enable rapid processive DNA replication. Enabled by the clamp-loading complex, the two beta subunits form a ring-like clamp around DNA and keep the polymerase sliding along. Given the essential role of beta-clamp, its inhibitors have been explored for antibacterial purposes. Similarly, beta-clamp is an ideal target for bacteriophages to shut off host DNA synthesis during host takeover. The Gp168 protein of phage Twort is such an example, which binds to the beta-clamp of Staphylococcus aureus and prevents it from loading onto DNA causing replication arrest. Here, we report a cryo-EM structure of the clamp-Gp168 complex at 3.2-A resolution. In the structure of the complex, the Gp168 dimer occupies the DNA sliding channel of beta-clamp and blocks its loading onto DNA, which represents a new inhibitory mechanism against beta-clamp function. Interestingly, the key residues responsible for this interaction on the beta-clamp are well conserved among bacteria. We therefore demonstrate that Gp168 is potentially a cross-species beta-clamp inhibitor, as it forms complex with the Bacillus subtilis beta-clamp. Our findings reveal an alternative mechanism for bacteriophages to inhibit beta-clamp and provide a new strategy to combat bacterial drug resistance. Bacteriophage Twort protein Gp168 is a beta-clamp inhibitor by occupying the DNA sliding channel.,Liu B, Li S, Liu Y, Chen H, Hu Z, Wang Z, Zhao Y, Zhang L, Ma B, Wang H, Matthews S, Wang Y, Zhang K Nucleic Acids Res. 2021 Nov 8;49(19):11367-11378. doi: 10.1093/nar/gkab875. PMID:34614154[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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