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

Radiolabelled glucuronoxylan was formed by incubation of a Golgi membr ane fraction from pea seedlings with UDP-(C-14)GlcA and UDP-Xyl. Chela tor-soluble glucuronoxylan was analysed by gel filtration on Sepharose CL-6B and CL-2B, and was resolved into a very high molecular weight p eak (at least 7000 kDa) and a partially-excluded peak (50-75 kDa). Tre atment 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 h igh temperature or by high salt concentration, and was probably covale nt. When radioactive glucuronoxylan was formed using endoplasmic retic ulum rather than Golgi membranes, protease treatment caused a decrease in molecular weight of approximately 20 kDa. The chelator-insoluble g lucuronoxylan produced by pea membranes was also partly susceptible to protease treatment, since almost half of it was solubilized by incuba tion with proteinase K.