AN AGAROSE-GEL ELECTROPHORESIS METHOD FOR THE SEPARATION OF ARABINOGALACTAN PROTEINS

A method for resolving plasma membrane associated arabinogalactan prot eins (AGPs) has been developed. Plasma membranes purified by aqueous p olymer two-phase partitioning were first subjected to Triton X-114 fra ctionation. The resulting water phase contained all detectable plasma membrane-bound AGPs. Plasma membrane AGPs were then resolved in an SDS -agarose gel electrophoresis system (SDS-AGE). For separating plasma m embrane AGP species of the same apparent molecular weight but with dif ferent net charge, a two-dimensional electrophoresis system was used, utilizing isoelectric focusing in an immobilized pH gradient in the fi rst dimension and SDS-AGE in the second dimension. These methods enabl ed the separation of individual plasma membrane AGPs. In comparison, S DS-PAGE methods left AGPs as unresolved high molecular-weight smears. The methods described here may help to establish some basic features o f AGPs, such as the number, organization, and protein and carbohydrate characteristics of plasma membrane AGPs, as well as the relationship between plasma membrane and extracellular AGPs.