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Communication between subunits critical to DNA binding by hexameric helicase of bacteriophage T7.


ABSTRACT: The DNA helicase encoded by bacteriophage T7 consists of six identical subunits that form a ring through which the DNA passes. Binding of ssDNA is a prior step to translocation and unwinding of DNA by the helicase. Arg-493 is located at a conserved structural motif within the interior cavity of the helicase and plays an important role in DNA binding. Replacement of Arg-493 with lysine or histidine reduces the ability of the helicase to bind DNA, hydrolyze dTTP, and unwind dsDNA. In contrast, replacement of Arg-493 with glutamine abolishes these activities, suggesting that positive charge at the position is essential. Based on the crystallographic structure of the helicase, Asp-468 is in the range to form a hydrogen bonding with Arg-493 on the adjacent subunit. In vivo complementation results indicate that an interaction between Asp-468 and Arg-493 is critical for a functional helicase and those residues can be swapped without losing the helicase activity. This study suggests that hydrogen bonding between Arg-493 and Asp-468 from adjacent subunits is critical for DNA binding ability of the T7 hexameric helicase.

SUBMITTER: Lee SJ 

PROVIDER: S-EPMC2449338 | biostudies-literature | 2008 Jul

REPOSITORIES: biostudies-literature

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Communication between subunits critical to DNA binding by hexameric helicase of bacteriophage T7.

Lee Seung-Joo SJ   Qimron Udi U   Richardson Charles C CC  

Proceedings of the National Academy of Sciences of the United States of America 20080623 26


The DNA helicase encoded by bacteriophage T7 consists of six identical subunits that form a ring through which the DNA passes. Binding of ssDNA is a prior step to translocation and unwinding of DNA by the helicase. Arg-493 is located at a conserved structural motif within the interior cavity of the helicase and plays an important role in DNA binding. Replacement of Arg-493 with lysine or histidine reduces the ability of the helicase to bind DNA, hydrolyze dTTP, and unwind dsDNA. In contrast, rep  ...[more]

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