Purification and properties of a protein factor stimulating peptidoglycan synthesis in toluene- and Licl-treated Bacillus megaterium cells

Abstract

A protein factor, called PG-I, can be solubilized from toluene-treated Bacillus megaterium cells by LiCl extraction. After LiCl extraction, peptidoglycan synthesis by the toluene-treated cells is decreased. Protein PG-I can be added back to the extracted cells to stimulate peptidoglycan synthesis. This factor has now been purified 124-fold. It has a molecular weight of 42,000 as estimated by Sephadex gel filtration in the presence of 0.4 M KCl and 52,000 as determined by sodium dodecyl sulfate disc gel electrophoresis. Periodate-Schiff staining of the polyacrylamide gel indicates that factor PG-I is a glycoprotein. The reconstitution of LiCl-extracted cells requires Mg2+ with an apparent Km of 1.9 X 10(-3) M. The Mg2+ ions can be replaced by Ca2+ and by Mn2+ ions to some extent; Zn2+ and Cu2+ ions had no effect. The available data suggest that factor PG-I is essential for peptidoglycan synthesis and requires at least one thiol group for stimulatory activity.