Structure of the distal half of the bacteriophage T4 tail fiber

Abstract

Studies of T4 amber mutants defective in tail fiber assembly have allowed the antigens of the distal half of the T4 tail fiber to be divided into two classes, called B and C. Only a few of the antibodies directed against these antigens cross-react with the related phage, T2. By adsorbing these cross-reactive antigens, it has been possible to produce a T4-specific anti-BC serum, AS1. The product of gene 37, P37, is the major protein in the distal half-fiber. A series of T2-T4 hybrid phage has been isolated which carry part of P37 from T2 and part from T4. By testing the ability of these hybrids to block the activity of AS1, it has been possible to divide the C antigen into 4 or 5 subclasses which have different specificities and are determined by different parts of P37. Observation of the tail fiber-antibody complexes formed by these hybrids and AS1 has allowed a determination of the topology of P37 in the assembled fiber. It is oriented linearly with its N-terminus near the joint between the two half-fibers and its C-terminus near the tip of the fiber. These observations lead to a simple model for the structure of the distal half-fiber.