Studies on biosynthesis of biological macromolecules using mutants of Escherichia coli.

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We studied the biosynthetic reactions of macromolecules and the genes controlling them in Escherichia coli, an ideal system for the basic cell research, aiming at understanding the mechanisms of cell replication and their genetic regulations.Scince the total number of genes is supposed to be several thousands in E. coli, we can expect to get at least one mutant for every gene if we isolate ten thousand mutants. Hirota isolated more than five thousand temperature-sensitive mutants of independent origin at random. We studied biosynthetic processes of macromolecules and their genetic controls using mutants found in Hirota's mutant collection.Hara and Hirota demonstrated that penicillin-binding protein (PBP)-3, an indispensable enzyme for cell division, is a protein translocated (secreted) across the membrane and is a lipoprotein in part. They found mutants defective in the processing of PBP-3 and studied the processing reaction. Ito identified the secY gene product involved in the secreti … More on of cell surface proteins and clarified its structure and function. He found and analyzed novel mutants defective in secretion process. Mizushima revealed the regulatory mechanism of expression of ompF and ompC, genes encoding the outer membrane proteins whose relative amounts are changed in response to the medium osmolarity, by determining the structures of their promoter regions and by analyzing their controlling factors, OmpR and EnvZ proteins. Nishino found mutants defective in biosynthesis of isoprenoids involved in the synthesis of cell wall, showed which enzyme is deficient in each mutant, and performed genetic analyses. Suzuki confirmed that, among the three components, <alpha> , <beta> and <gamma> of PBP-1b participating in the growth of cell surface, <alpha> and <gamma> are the primary gene products and that <beta> is generated from <alpha> during preparation of the membrane fraction. He found a mutant defective in the <alpha> -> <beta> conversion and determined the structures of these components. Less