The T4 phage SF1B helicase Dda is structurally optimized to perform DNA strand separation.
Helicases move on DNA via an ATP binding and hydrolysis mechanism coordinated by well-characterized helicase motifs. However, the translocation along single-stranded DNA (ssDNA) and the strand separation of double-stranded (dsDNA) may be loosely or tightly coupled. Dda is a phage T4 SF1B helicase with sequence homology to the Pif1 family of helicases that tightly couples translocation to strand separation. The crystal structure of the Dda-ssDNA binary complex reveals a domain referred to as the "pin" that was previously thought to remain static during strand separation. The pin contains a conserved phenylalanine that mediates a transient base-stacking interaction that is absolutely required for separation of dsDNA. The pin is secured at its tip by protein-protein interactions through an extended SH3 domain thereby creating a rigid strut. The conserved interface between the pin and the SH3 domain provides the mechanism for tight coupling of translocation to strand separation.
He, X; Byrd, AK; Yun, M-K; Pemble, CW; Harrison, D; Yeruva, L; Dahl, C; Kreuzer, KN; Raney, KD; White, SW
Volume / Issue
Start / End Page
Pubmed Central ID
Electronic International Standard Serial Number (EISSN)
Digital Object Identifier (DOI)