Mercurials and red cell membranes

Mercurials influence a large number of protein-mediated functions in membranes including transport phenomena, related enzyme activities and sructural factors such as deformability and phospholipid asymmetry. The sulfhydryl groups that are the targets for mercurials are found in different locations in the membrane, the outer surface, internal compartments, or cytoplasmic surface. Those on the outer surface are immediately influenced even by non-penetrating mercurials, whereas those within the membrane are only accessible after a time delay, to permeating agents. Agents that permeate very rapidly will equilibrate with internal proteins (hemoglobin) producing small transient effects on the membrane, whereas agents that penetrate slowly will produce larger more prolonged effects. The mode of penetration is of importance. Sulfhydryl groups within an intrinsic protein channel will only be affected if the mercurial can penetrate into that channel. Although all mercurials can react with high specificity with sulfhydryl groups, structural factors relating to the membrane architecture and the capacity of different agents to penetrate into the membrane, lead to considerable diversity in their effectiveness against particular functions. Mercurials with different capacities to penetrate can be effective tools in determining the arrangement of functional proteins in the membrane and in determining how they work.