Bacteriophage lambda preconnectors. Purification and structure

J Mol Biol. 1984 Apr 15;174(3):433-47. doi: 10.1016/0022-2836(84)90330-9.


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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Bacteriophage lambda / analysis*
  • Bacteriophage lambda / ultrastructure
  • Electrophoresis, Polyacrylamide Gel
  • Filtration
  • Image Enhancement
  • Microscopy, Electron
  • Models, Molecular
  • Viral Proteins / isolation & purification*


  • Viral Proteins