Pvn. Bodine et G. Litwack, PURIFICATION OF THE GLUCOCORTICOID RECEPTOR-MINERALOCORTICOID RECEPTOR MODULATOR-2 FROM RABBIT LIVER, Receptor, 5(3), 1995, pp. 133-143
Modulators-1 and -2 are endogenous low-mel-wt regulators of glucocorti
coid and mineralocorticoid receptors and protein kinase C. Structural
analysis of apparently purified modulators suggested that these molecu
les were novel ether aminophosphoglycerides. Subsequent X-ray crystall
ography and NMR spectroscopy indicated that the ultra-large scale modu
lator preparations were contaminated with glutamate and aspartate, alt
hough these amino acids lacked modulator activity. In this article, we
describe the purification of modulator-2 from rabbit liver cytosol an
d the separation of this phosphoglyceride from these amino acids. This
purification was similar to the ultra-large scale version (Bodine, P.
V. and Litwack, G. [1990] J. Biol. Chem. 265, 9544-9554), but involve
d the chromatography of trypsinized rabbit liver cytosol on the 7-L be
d volume Sephadex G-15 gel-filtration column. As before, two peaks of
modulator activity (modulator-1 and -2), as well as a DNA-binding inhi
bitor (peak-3), eluted from the gel-filtration column. The resulting m
odulator-2 pool was incubated with glutamate decarboxylase and treated
batch-wise with Dowex-50W cation-exchange resin and Chelex-100 resin.
This enzyme/resin-treated modulator-2 preparation was then chromatogr
aphed on a Dowex-l anion-exchange column. Finally, modulator-2 was pur
ified by preparative silica TLC. This last purification step resulted
in the separation of modulator-2 from glutamate, aspartate, and gamma-
aminobutyrate. In summary, rabbit liver cytosol appears to be a reason
able source of modulator-2. In addition, treatment of the preparation
with glutamate decarboxylase seems to facilitate the subsequent separa
tion of modulator-2 from the contaminating amino acids.