Selective Solubilization of Microsomal Electron-Transfer Proteins with Alkyiglucoside

Abstract

A series of alkylglucosides (AGs) was examined for the solubilization of four microsomal electron-transfer proteins (cytochrome P450 (P450), cytochrome b₅ (b₅), NADPH-cytochrome P450 reductase (fp2), and NADH-cytochrome b₅ reductase (fp1)) in rat liver microsomes. Among the four proteins, b₅ and fp2 were completely solubilized, and thus, almost recovered in the supernatant fraction after centrifugation, while P450 and fp1 were in the pellet. In particular, the solubilization yield of P450 was only about 10%. With a high ratio of alkylglucoside to membrane, along with a low ionic strength, a greater selectivity for b₅ and fp2 could be obtained. Such high selectivity was not observed by the use of sugar ester, bile salt, and poly(oxyethylene) alkylphenyl ether types of surfactants. After re-solubilization of the pellet with sodium cholate, the supernatant fraction contained P450 free from b₅ and the final recovery of P450 was about 40%. Thus, this two-step solubilization provides a simple method for the partial purification of P450 in microsomes.