Crystal structure of T7 gene 4 ring indicates a mechanism for sequential hydrolysis of nucleotides

Martin R. Singleton, Michael R. Sawaya, Tom Ellenberger, Dale B. Wigley

Research output: Contribution to journalArticle

399 Scopus citations

Abstract

We have determined the crystal structure of an active, hexameric fragment of the gene 4 helicase from bacteriophage T7. The structure reveals how subunit contacts stabilize the hexamer. Deviation from expected six-fold symmetry of the hexamer indicates that the structure is of an intermediate on the catalytic pathway. The structural consequences of the asymmetry suggest a 'binding change' mechanism to explain how cooperative binding and hydrolysis of nucleotides are coupled to conformational changes in the ring that most likely accompany duplex unwinding. The structure of a complex with a nonhydrolyzable ATP analog provides additional evidence for this hypothesis, with only four of the six possible nucleotide binding sites being occupied in this conformation of the hexamer. This model suggests a mechanism for DNA translocation.

Original languageEnglish
Pages (from-to)589-600
Number of pages12
JournalCell
Volume101
Issue number6
DOIs
StatePublished - Jun 9 2000

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