Arsenic-lipid complex formation during sugar transport

During a study of the mechanism of transport of sugars in Nocardia, it was found that sodium arsenate was able to restore the phosphate-requiring glucose uptake.

On examination of the distribution of arsenic in the cells, it was found that the cellular residue obtained after lipid extraction shows only traces of arsenic (1.0 μg/250 mg of cells) as against 15.0 μg of arsenic in the corresponding lipid extract (chloroform-methanol, 2:1, v/v).

After separation of the acetone precipitable and soluble lipids, all the arsenic remains in the polar fraction. This arsenic was not liberated into the water after orientation of the polar lipids in a water-lipid interphase during a period of 18–24 h.

A preliminary identification of the polar lipids of Nocardia by a silicic acid column, paper and thin-layer chromatography shows that the arsenic appears to be associated with at least two different spots with R_F values similar to those of phosphoinositols and sphingomyelin-type compounds.

Arsenic-lipid complex formation as a possible component of a carrier system in sugar transport in Nocardia is discussed.