This family includes bacteriophage, plasmid and bacterial helicases. All of them are involved in DNA replication and are associated with DNA primase, either interacting with a primase protein or showing primase activity themselves.
P is very likely to be the phage-encoded replication fork helicase.
Our group has used electron microscopy of negatively stained G 40 P samples and image processing techniques to study the structural characteristics of the hexameric assemblies of this protein. We also proposed a new approach for the analysis of rotational symmetry heterogeneities, which allowed the detection of different quaternary organizations of the protein, without assuming any a priori rotational symmetry of the oligomers. Our results provided the first low resolution structural data for a hexameric helicase of Gram-postive bacterial origin. The white arrowheads point to some characteristic particles selected from the micrographs. The gallery on the right-hand side shows the sort of single particle images obtained, enclosed in frames of 19 nm x 19 nm.