PROPERTIES OF A PROTEIN-LINKED GLUCURONOXYLAN FORMED IN THE PLANT GOLGI-APPARATUS

Radiolabelled glucuronoxylan was formed by incubation of a Golgi membrane fraction from pea seedlings with UDP-(C-14)GlcA and UDP-Xyl. Chelator-soluble glucuronoxylan was analysed by gel filtration on Sepharose CL-6B and CL-2B, and was resolved into a very high molecular weight peak (at least 7000 kDa) and a partially-excluded peak (50-75 kDa). Treatment of the latter peak with proteinase K caused a change in elution behaviour corresponding to the removal of a protein of 36-45 kDa. The association between polysaccharide and protein was not disrupted by high temperature or by high salt concentration, and was probably covalent. When radioactive glucuronoxylan was formed using endoplasmic reticulum rather than Golgi membranes, protease treatment caused a decrease in molecular weight of approximately 20 kDa. The chelator-insoluble glucuronoxylan produced by pea membranes was also partly susceptible to protease treatment, since almost half of it was solubilized by incubation with proteinase K.