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Structure of T4 Bacteriophage clamp loader bound to the T4 clamp, primer-template DNA, and ATP analog
Structural highlights
FunctionLOADS_BPT4 Forms the sliding-clamp-loader together with the small subunit (PubMed:10585481). The clamp loader holds the clamp in an open conformation and places it onto the DNA (PubMed:22194570).[HAMAP-Rule:MF_04163][1] [2] Publication Abstract from PubMedClamp loaders are AAA+ ATPases that facilitate high-speed DNA replication. In eukaryotic and bacteriophage clamp loaders, ATP hydrolysis requires interactions between aspartate residues in one protomer, present in conserved 'DEAD-box' motifs, and arginine residues in adjacent protomers. We show that functional defects resulting from a DEAD-box mutation in the T4 bacteriophage clamp loader can be compensated by widely distributed single mutations in the ATPase domain. Using cryo-EM, we discovered an unsuspected inactive conformation of the clamp loader, in which DNA binding is blocked and the catalytic sites are disassembled. Mutations that restore function map to regions of conformational change upon activation, suggesting that these mutations may increase DNA affinity by altering the energetic balance between inactive and active states. Our results show that there are extensive opportunities for evolution to improve catalytic efficiency when an inactive intermediate is involved. Autoinhibition of a clamp-loader ATPase revealed by deep mutagenesis and cryo-EM.,Marcus K, Huang Y, Subramanian S, Gee CL, Gorday K, Ghaffari-Kashani S, Luo XR, Zheng L, O'Donnell M, Subramaniam S, Kuriyan J Nat Struct Mol Biol. 2024 Mar;31(3):424-435. doi: 10.1038/s41594-023-01177-3. , Epub 2024 Jan 4. PMID:38177685[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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