title: Bacteriophage lambda preconnectors. Purification and structure.
abstract: The morphogenesis of bacteriophage lambda proheads is under the control of the four phage genes B, C, Nu3 and E, and the two Escherichia coli genes groEL and groES . It has been shown previously that extracts prepared from cells infected with a lambda C-E- mutant accumulate a gpB polymer, which behaves as a biologically active intermediate in prohead assembly. This gpB activity has been called a preconnector , as it is probably a precursor to the head-tail connector. We now report the partial purification of biologically active preconnectors and the characterization of its structure. In the electron microscope, preconnectors appear as donut -like structures composed of several subunits displaying radial symmetry. Optical filtration of periodic arrays of preconnectors showed that the structure has 12-fold rotational symmetry. Side views of the preconnector reveal that it resembles an asymmetrical dumbell . This information has been used to construct a three-dimensional model of the preconnector . The implications of this structure for prohead shape and function, and for DNA packaging are discussed.
mesh_terms: D010582:Bacteriophage lambda / Q000032:analysis* / Q000648:ultrastructure; D004591:Electrophoresis, Polyacrylamide Gel; D005374:Filtration; D007089:Image Enhancement; D008854:Microscopy, Electron; D008958:Models, Molecular; D014764:Viral Proteins / Q000302:isolation & purification*
chemical_list: D014764:Viral Proteins