A genetic analysis of bacteriophage λ head assembly

Abstract

The sequence of steps involved in bacteriophage λ head assembly has been studied by characterizing second-site mutatons that can compensate for the reduced level of synthesis of a particular phage “head” protein. Such studies reveal these classes of protein interactions: (1) A reduced level of either pA synthesis or activity can compensate for the reduced amount of pD made when λD am mutants are grown in a supC host. This result implies that pA acts before pD during the packaging of phage DNA. (2) A reduced level of either pB synthesis or activity can compensate for the reduced amount of pE made when λE am mutants are grown in a supC host, and vice versa. This result suggests an interaction between these proteins that is stringently dependent on maintaining a proper ratio between them. An identical argument has been made to explain the properties of groE hosts (Sternberg, 1973). (3) A very specific class of mutations in phage gene E can compensate for the reduced amount of pC made when λC am mutants are grown in a supC host. This suggests that the products of these two genes directly interact. Using the techniques described in this report it is possible to easily isolate a variety of mutations ( am, oc, ts, and missense) in specific phage “head” genes (genes A, B and E).