6jir | pdb_00006jir
Crystal structure of C. crescentus beta sliding clamp with PEG bound to putative beta-motif tethering region
Structural highlights
Function[DPO3B_CAUVC] 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 PubMedThe eubacterial beta sliding clamp (DnaN) plays a crucial role in DNA metabolism through direct interactions with DNA, polymerases and a variety of protein factors. A canonical protein-DnaN interaction has been identified in Escherichia coli and some other species, during which protein partners are tethered into the conserved canonical hydrophobic crevice of DnaN via the consensus beta-binding motif. Caulobacter crescentus is an excellent research model for use in the investigation of DNA replication and cell cycle regulation due to its unique asymmetric cell division pattern with restricted replication initiation; however, little is known about the specific features of C. crescentus DnaN (CcDnaN). Here, we report a significant divergence in the association of CcDnaN with proteins based on docking analysis and crystal structures that show that the beta-binding motifs of its protein partners bind a novel pocket instead of the canonical site. Pull-down and isothermal titration calorimetry (ITC) results revealed that mutations within the novel pocket disrupt protein-CcDnaN interactions. It was also shown by replication and RIDA (regulatory inactivation of DnaA) assays that mediation of protein interaction by the novel pocket is closely related to the performance of CcDnaN during replication and the DnaN-mediated regulation process. Moreover, assessments of clamp competition showed that DNA does not compete with protein partners when binding to the novel pocket. Overall, our structural and biochemical analyses provide strong evidence that CcDnaN employs a noncanonical protein association pattern. Caulobacter crescentus beta sliding clamp employs a noncanonical regulatory model of DNA replication.,Jiang X, Zhang L, An J, Wang M, Teng M, Guo Q, Li X FEBS J. 2019 Nov 14. doi: 10.1111/febs.15138. PMID:31725950[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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