The location of arabinosyl:hydroxyproline transferase in the membrane system of potato tissue culture cells

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Abstract
Incubation of a particulate preparation from potato tissue culture cells with UDP-.beta.-L-[1-3H]arabinose yielded a glycoprotein fraction containing labeled material with the characteristics of hydroxyproline arabinosides. The sugar-protein linkage was resistant to hot alkaline hydrolysis and the hydrolytic products showed similar electrophoretic and chromatographic behavior to authentic hydroxyproline-arabinosides prepared from potato tissue culture cell walls. Incorporation of arabinose into glycoprotein was stimulated by the addition of de-arabinosylated potato lectin. The product of the incubation co-migrated with native potato lectin on sodium dodecyl sulfate/polyacrylamide-gel electrophoretics. The subcellular distribution of the arabinosyltransferase was investigated by fractionating potato tissue culture membranes on a discontinuous sucrose gradient in the presence or absence of Mg2+. Under both fractionation conditions the highest specific activity of the enzyme was found in the Golgi-enriched fraction. The results are discussed in relation to the synthesis of the hydroxyproline-rich glycoprotein component of plant cell walls.