Distinct roles for ATP binding and hydrolysis at individual subunits of an archaeal clamp loader

• Published in: The EMBO journal Vol. 23; no. 6; pp. 1360 - 1371
• Main Authors: Seybert, Anja, Wigley, Dale B
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 24.03.2004; Blackwell Publishing Ltd
• Subjects: Adenosine Triphosphatases - metabolism; Adenosine Triphosphate - metabolism; Archaea; ATP; ATP hydrolysis; Catalysis; clamp loader; Deoxyribonucleic acid; DNA; DNA Polymerase III - chemistry; DNA Polymerase III - metabolism; DNA, Archaeal - metabolism; DNA-Binding Proteins - chemistry; DNA-Binding Proteins - metabolism; Euryarchaeota - genetics; Euryarchaeota - metabolism; Hydrolysis; Models, Biological; Mutation - genetics; nucleotide binding; Nucleotides - metabolism; PCNA; Proliferating Cell Nuclear Antigen - metabolism; Protein Subunits - chemistry; Protein Subunits - metabolism; replication; Replication Protein C
• ISSN: 0261-4189; 1460-2075
• DOI: 10.1038/sj.emboj.7600130

Circular clamps are utilised by replicative polymerases to enhance processivity. The topological problem of loading a toroidal clamp onto DNA is overcome by ATP‐dependent clamp loader complexes. Different organisms use related protein machines to load clamps, but the mechanisms by which they utilise ATP are surprisingly different. Using mutant clamp loaders that are deficient in either ATP binding or hydrolysis in different subunits, we show how the different subunits of an archaeal clamp loader use ATP binding and hydrolysis in distinct ways at different steps in the loading process. Binding of nucleotide by the large subunit and three of the four small subunits is sufficient for clamp loading. However, ATP hydrolysis by the small subunits is required for release of PCNA to allow formation of the complex between PCNA and the polymerase, while hydrolysis by the large subunit is required for catalytic clamp loading.