Influence of fatty acids on the electrophoretic behavior of proteins with special reference to pituitary hormone and thyroglobulin.

Fatty acids in a 30,000 to 100,000 x g ultracentrifugal pellet from pituitary glands, liver, and muscle were found to be responsible for an observed alteration of the disc electrophoretic behavior of a number of proteins. Three principal fatty acids were found in the pellet (oleic, palmitic, and stearic) and, of the three, oleic was the most effective in causing the alteration. When analyzed electrophoretically (pH 9.5) with fatty acid or the ultracentrifugal pellet, prolactin and growth hormone, as well as hemoglobin and myoglobin, were converted to forms that migrated in the pre-albumin area and at the electrophoretic buBer front. Aggregated prolactin dissociated to lower molecular weight material; the 19 S component of thyroglobulin was converted to the 12 S form, together with higher molecular weight substances. Muscle aldolase, which normally migrates as one electrophoretic component, showed at least four new bands when analyzed with oleic acid. Alteration of the electrophoretic pattern could be demonstrated with the 100,000 x g pellet before extraction of fatty acids, and even with some crude extracts. Addition of ethylenediaminetetraacetate to extracts or ultracentrifugal pellets increased the amount of alteration but was without effect when purified fatty acids were used. Deozycholate and divalent metal ions prevented alteration in all cases. Modification of electrophoretic patterns by the extracts and pellets was proportional to the sample height if the disc electrophoretic method was used and was minimal when the concentrating gel was eliminated. Sample height effects were not detectable when purified fatty acids were used. Alteration of electrophoretic pattern occurred only under alkaline conditions. Serum albumin and transfer-r-in were unaffected. No alteration of the electrophoretic patterns was caused when red cell stroma or bacterial cell wall was mixed with purified proteins.