Formation of glucuronoxylan linked to protein in plant Golgi and plasma membranes.

It has been suggested that proteins act as primers for the synthesis of polysaccharides in general [ 11 and for plant-cellwall polysaccharides in particular 121. These primer proteins might anchor nascent matrix polysxcharides to the membrane during their passage through the endomembrane system from the Golgi apparatus to the cell wall 131. In this paper we give e v i d e n c e f o r a p r o t e i n p r i m e r for t h e s y n t h e s i s of glucuronoxylan. a plant-cell-w>all matrix polysaccharide, and show that this protein is attached to nascent glucuronoxylan in different parts of the endomembr;ine system. A par t iculate enz; m e preparat ion was obtalned f r o m etiolated pea seedlings and solubilised i n 10% (w/v) Triton X100 as descr ed 141. The enzyme (0.5niI) was incubated with