Structural Components of Bacteriophage

A procedure is described for the efficient disjoining of the even-numbered T bacteriophages into structural components. Tail fibres and tail sheaths from T2L have been separated and purified, and sheaths can be obtained from the other T-even phages. The components have been characterized by electron microscopy using the phosphotungstate method and by chemical and physical methods. The tail of the bacteriophage consists of a sheath surrounding a core at the base of which are attached tail fibres. The sheath appears to be built of helically arranged subunits which form a hollow cylinder. We have confirmed that the sheath can contract in length, and have shown that the contraction is accompanied by an increase in diameter such that the volume of the sheath is approximately conserved. The core of the tail has been found to be a hollow cylinder with the central hole 25 A in diameter. Chemical studies, using fingerprinting, suggest that the sheath is composed of about 200 repeated subunits of approximately 50,000 molecular weight. No N-terminal amino acid could be detected in sheaths. Fingerprints confirm the previous finding that the head membrane of the phage is composed of a large number of repeated subunits with a molecular weight of 80,000. The tail fibres appear to have a subunit with a molecular weight not less than 100,000. These studies show that the proteins composing the head, sheath and tail fibres of the phage have different primary structures.