Structural polypeptides and products of late genes of bacteriophage Mu: Characterization and functional aspects

Abstract

This paper describes the identification and functional role of late gene products of bacteriophage Mu, including an analysis of the structural proteins of the Mu virion. In vitro reconstitution of infectious phage particles has shown that four genes ( E, D, I, J) control the formation of phage heads and that a cluster of eight genes ( K, L, M, N, P, Q, R, S) controls the formation of phage tails. Sodium dodecyl sulphate/polyacrylamide gel electrophoresis of Mu polypeptides synthesized in Escherichia coli minicells infected by Mu phages carrying amber mutations in various late genes has resulted in the identification of the products of gene C (15.5 × 10 3 M r); H (64 × 10 3 M r); F (54 × 10 3 M r); G (16 × 10 3 M r); L (55 × 10 3 M r); N (60 × 10 3 M r); P (43 × 10 3 M r) and S (56 × 10 3 M r). Minicells infected with λpMu hybrid phages and deletion mutants of Mu were used to identify polypeptides encoded by the V-β region of the Mu genome. These are the products of genes V, W or R (41.5 × 10 3 M r, and 45 × 10 3 M r); U (20.5 × 10 3 M r) and of genes located in the β region (24 × 10 3 M r (gp gin) and 37 × 10 3 M r (possibly gp mom)). Analytical separation of the proteins of the Mu virion revealed that it consists of a major head polypeptide with a molecular weight of 33 × 10 3, a second head polypeptide of 54 × 10 3 (gp F) and two major tail polypeptides with molecular weights of 55 × 10 3 and 12.5 × 10 3 (gp L and gp Y, respectively). In addition, there are five minor components of the tail (including gp N, gp S and gp U) and approximately seven minor components of the head structure of the virion (including gp H).