Caulobacter crescentus β sliding clamp employs a noncanonical regulatory model of DNA replication. (29th November 2019)

• Record Type: Journal Article
• Authors: Jiang, Xuguang; Zhang, Linjuan; An, Jiancheng; Wang, Mingxing; Teng, Maikun; Guo, Qiong; Li, Xu
• Is Part Of: FEBS journal. Volume 287:Number 11(2020)
• Page Start: 2292
• Page End: 2311
• Publication Date: 2019-11-29
• Subjects: Caulobacter crescentus -- DNA replication -- hydrophobic pocket -- β sliding clamp -- β‐binding motif; Biochemistry -- Periodicals; Molecular biology -- Periodicals; Pathology, Molecular -- Periodicals; 572
• DOI: 10.1111/febs.15138
• Languages: English
• ISSNs: 1742-464X

Abstract

Abstract : The eubacterial β 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 β‐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 ( Cc DnaN). Here, we report a significant divergence in the association of Cc DnaN with proteins based on docking analysis and crystal structures that show that the β‐binding motifs of its protein partners bind a novel pocket instead of the canonical site. Pull‐down and isothermal titration calorimetry results revealed that mutations within the novel pocket disrupt protein– Cc DnaN interactions. It was also shown by replication and regulatory inactivation of DnaA assays that mediation of protein interaction by the novel pocket is closely related to the performance of Cc DnaN 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 Cc DnaN employs a noncanonical protein association pattern. Abstract : A structural and biochemical analysis was performed on the eubacterial β sliding clamp (DnaN) of Caulobacter crescentus . Results found a noncanonical protein binding pocket on the lateral side, which substitutes the canonical C‐terminal pocket for β motif‐mediated protein interaction of Cc DnaN, resulting in the distinct biochemical features of Cc DnaN and potentially leading to a difference in performance of Cc DnaN during replication and the DnaN‐mediated regulation process in C. crescentus .