Molecular Cloning, Sequencing, and Expression of Two Late Proteins of Bacteriophage MB78

Abstract

Bacteriophage MB78, a virulent phage of Salmonella typhimurium, does not allow other phages, such as P22 and 9NA, to grow in its presence. A detailed physical map of this phage has been constructed in our laboratory. In an ongoing effort to understand the genetics of this interesting phage, various genes were characterized. Here, we report cloning, sequencing, and expression of two late proteins, coded in a Sal I‐ Hind III fragment (SH9), by using the minicell expression system. Further, we performed a kinetic study of phage proteins by infecting the host LT2 cells and compared the proteins produced, with proteins obtained by the minicell expression system. Both sets of proteins run exactly parallel and migrated as 14‐ and 15‐kDa proteins on a polyacrylamide gel. The synthesis of these two proteins started 15 min after infection with MB78 and was prominent after 45 min. One of the proteins exhibited 57% homology to the structural protein of mycobacteriophage L5.