Structure and inherent properties of the bacteriophage lambda head shell: VI. DNA-packaging-defective mutants in the major capsid protein

Abstract

Some amino acid substitutions in the major capsid protein (gene E product) of lambda phage are found to cause a defect in DNA packaging. These substitutions permit initiation of DNA packaging and expansion of the prohead. However, cleavage of the concatemer DNA at the cos site takes place only to a very small extent, and the capsid eventually becomes empty. Interestingly, the mutations are suppressed by a decrease of the DNA length between the cos sites by 8000 to 10,000 bases. These properties are similar to those of amber mutants in gene D, which codes for the capsid outer-surface protein. Studies on the E missense D amber double mutant show that the E protein and the D protein contribute additively to the stabilization of the condensed form of the DNA molecule in phage heads.