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

A protein factor, called PG I, can be solubilized from toluene treated B. 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 K(m) of 1.9x10^-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.