The transformation of tau particles into T4 heads. II. Transformations of the surface lattice and related observations on form determination.

In part I of this paper (1) we give evidence that the P23-capsoid of τ-particles is transformed in situ into the P23*-capsid of normal phage. Using the polymorphism of phage T4, we have chosen polyheads as representative of P23 assemblies and giant phages as representative of P23* assemblies in order to study their surface crystals by optical filtration of micrographs. We found for polyheads a lattice constant of 112 A with the typical hexameric, ringlike capsomer and for the giants a lattice constant of 124 A with quite a different capsomer morphology, of the type (6+1). From the stoichiometry of the proteins composing the normal capsid we conclude that the protomer is a single P23* molecule and that the minor capsid-proteins must be in singular positions on the surface lattice or on the polyhedral head (center of capsomers, vertices, or basal part). We extrapolate the findings on the giant head to the normal head and give a geometric model which is consistent with 1,100 molecules of P23* per capsid. We discuss the part of form inheritance contributed by P23 and the other formgiving gene products and give evidence that morphologic characters are the result of pairs of a reaction chain of interacting gene products. The example we give is the giant head produced by a ts mutant in gene 24 at 36°C.