Complex Enzyme Systems into Membranes in the Absence of Phospholipid Synthesis

Integration of Complex Enzyme Systems into Membranes in the Absence of Phospholipid Synthesis 

aureus has an inducible system for the transport and breakdown of galactosides. The transport system has been characterized as a phospho- 

Upon induction of the lac system, the synthesis of phospho-/ -galac-tosidase activity and galactoside transport activity increase coordinately. In 

The permease can be measured as a phosphotransferase activity in vitro, as well as a transport system in vivo. Membranes isolated from cells induced for the lac system in the absence of lipid synthesis were prepared, and phosphotransferase activity was measured. It was found that the phosphotransferase activity of membranes from glycerol-deprived cells, when normalized to j -galactosidase activity of the culture, was identical to that of the supplemented cells, indicating that the Enzyme II component of the /flc-transport system was, in fact, synthesized at the same rate with respect to j -galactosidase activity in both the deprived and the supplemented cultures (Fig. 8). The results also indicate that Enzyme II is integrated into the membrane to the same extent, in both deprived and supplemented cultures. 

The addition of chloramphenicol to a deprived culture causes a cessation in the increase in both the galactosidase and permease activities. However, if chloramphenicol and glycerol are added to a deprived culture, the galactosidase activity does not increase, whereas the permease activity increases slowly until it approaches values characteristic of a supplemented culture (Fig. 9). The demonstration of normal phosphotransferase activity in the membranes of cells induced for the lac system in the absence of lipid synthesis is consistent with previously discussed data showing that other membrane-bound systems can be integrated into the membrane in a functional manner. The low efficiency of the deprived cells in transport, though, indicates that there exists some requirement for lipid synthesis for the effi- 

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