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When a helicase is not a helicase: dsDNA tracking by the motor protein Eco R124I
Author(s) -
Stanley Louise K,
Seidel Ralf,
van der Scheer Carsten,
Dekker Nynke H,
Szczelkun Mark D,
Dekker Cees
Publication year - 2006
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1038/sj.emboj.7601104
Subject(s) - helicase , biology , dna , chromosomal translocation , biophysics , molecular motor , rna helicase a , enzyme , biochemistry , gene , rna
Using a combination of single molecule and bulk solution measurements, we have examined the DNA translocation activity of a helicase, the Type I restriction modification enzyme Eco R124I. We find that Eco R124I can translocate past covalent interstrand crosslinks, inconsistent with an obligatory unwinding mechanism. Instead, translocation of the intact dsDNA occurs principally via contacts to the sugar‐phosphate backbone and bases of the 3′–5′ strand; contacts to the 5′–3′ strand are not essential for motion but do play a key role in stabilising the motor on the DNA. A model for dsDNA translocation is presented that could be applicable to a wide range of other enzyme complexes that are also labelled as helicases but which do not have actual unwinding activity.