Communication between subunits critical to DNA binding by hexameric helicase of bacteriophage T7.
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.
Lee
Seung-Joo
SJ
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA.
Qimron
Udi
U
Richardson
Charles C
CC
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D017123:Bacteriophage T7 / Q000201:enzymology*; D004247:DNA / Q000378:metabolism*; D004265:DNA Helicases / Q000737:chemistry* / Q000378:metabolism*; D019915:DNA Primase / Q000378:metabolism; D004926:Escherichia coli / Q000821:virology; D006868:Hydrolysis; D008969:Molecular Sequence Data; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism*; D013942:Thymine Nucleotides / Q000378:metabolism; D014764:Viral Proteins / Q000737:chemistry* / Q000378:metabolism*
D021122:Protein Subunits; D013942:Thymine Nucleotides; D014764:Viral Proteins; D004247:DNA; D019915:DNA Primase; D004265:DNA Helicases; C024157:thymidine 5'-triphosphate