Properties of a protein-linked glucuronoxylan formed in the plant Golgi apparatus

Radiolabelled glucuronoxylan was formed by incubation of a Golgimembrane fraction from pea seedlings with UDP-(¹⁴C)GlcA andUDP-Xyl. Chelator-soluble glucuronoxylan was analysed by gelfiltration on Sepharose CL-6B and CL-2B, and was resolved intoa very high molecular weight peak (at least 7000 kDa) and apartially-excluded peak (50-75 kDa). Treatment of the latterpeak with proteinase K caused a change in elution behaviourcorresponding to the removal of a protein of 36-45 kDa. Theassociation between poly-saccharide and protein was not disruptedby high temperature or by high salt concentration, and was probablycovalent. When radioactive glucuronoxylan was formed using endoplasmicreticulum rather than Golgi membranes, protease treatment causeda decrease in molecular weight of approximately 20 kDa. Thechelator-insoluble glucuronoxylan produced by pea membraneswas also partly susceptible to protease treatment, since almosthalf of it was solubilized by incubation with proteinase K. Key words: Glucuronoxylan, Golgi apparatus, endoplasmic reticulum, Pisum