The Binding of Deoxycholate and Triton X-100 to Proteins

Deoxycholate and Triton X-100 resemble other anionic and neutral amphiphiles in binding to the high affinity sites of native bovine serum albumin. There are four principal sites for each ligand and about 14 weaker sites for deoxycholate; more than half the strong sites are common to each ligand, or octyl and dodecyl sulfates, or both, on the basis of competitive binding studies. On the other hand, cooperative binding of large amounts of ligand with accompanying denaturation, such as is observed for dodecyl sulfate and many other ionic detergents for serum albumin and most other proteins, does not take place with deoxycholate and Triton X-100. The probable reason is that these substances have a relatively low critical micelle concentration, so that a monomeric concentration sufficient for the cooperative mode of binding cannot be attained. The utility of deoxycholate and Triton X-100 for the solubilization of membrane proteins in native or near-native form is consistent with these results.