Crystal structures of complexes of PcrA DNA helicase with a DNA substrate indicate an inchworm mechanism.

摘要: We have determined two different structures of PcrA DNA helicase complexed with the same single strand tailed duplex, providing snapshots steps on catalytic pathway. One is a complex nonhydrolyzable analog ATP and thus "substrate" complex. The other structure contains bound sulphate ion that sits in position equivalent to occupied by phosphate produced after hydrolysis, thereby mimicking "product" In both complexes, protein monomeric. Large distinct conformational changes occur binding nucleotide cofactor. Taken together, these provide evidence against an "active rolling" model for action but are instead consistent "inchworm" mechanism.