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The Morphogenesis of the Phage Lambda Head: the Step Controlled by Gene F

Sherwood Casjens


Eighteen genes, all located in the left arm of the chromosome, control the morphogenesis of phage λ (Campbell, 1961; Parkinson, 1968; Mount et al., 1968). These can be divided into two distinct gene clusters by electron microscopic investigations (Mount et al., 1968; Kemp et al., 1968) and by utilization of the observation by Weigle (1966) that λ heads and tails can join in vitro to form infectious phage (Weigle, 1966; Parkinson, 1968). One cluster containing seven genes (A, W, B, C, D, E, and F), controls the formation of phage heads, and the other, containing eleven genes (Z, U, V, G, T, H, M, L, K, I, J), controls the synthesis of phage tails. Thus, the maximum number of phage-specified proteins present in the mature phage particle could be 18; however physicochemical studies of phage particles (Villarejo et al., 1967; Casjens et al., 1970; Buchwald et al., 1970; Murialdo and Siminovitch, this volume) have revealed only 3 major proteins and up to 8 minor protein species which can be reproducibly identified by sodium dodecylsulfate (SDS) gel electrophoresis (Table 1).

A more detailed description of the process of morphogenesis requires knowledge of the function performed by the products of each of these genes. Some progress toward this aim has been made by the identification of the products of several of these genes as components of the phage particle. Gene E appears to code for the synthesis of the major head protein (h2). Mutants in gene E...

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