Structure and inherent properties of the bacteriophage lambda head shell. II Isolation and initial characterization of prophage mutants defective in gene E

Prophage mutants defective in gene E of bacteriophage lambda were isolated and characterized to analyze the physiological functions of the major head protein (the gene E product). Seventy-one mutants were classified into the following five groups according to their phenotype under the electron microscope: two producing polyheads, two producing icosahedral structures and one producing no head-related structures detectable by electron microscopy. The former four phenotypes probably arose from defects in specific functional sites of the major head protein. Deletion mapping showed that some of the mutants belonging to the same phenotype mapped in distantly separated regions in gene E. Such regions may code for adjacent parts of the three-dimensional structure after folding of the polypeptide chain.