Rhamnogalacturonan-II--a biologically active fragment

Rhamnogalacturonan-II inhibited the uptake of ¹⁴C]leucine and,consequently, the incorporation of ¹⁴C]leucine into acid-precipitableproteins by suspension-cultured tomato cells. Fractionationof rhamnogalacturonan-II showed that the lower molecular componentswere the most effective. KDO and apiose, both constituents ofrhamnogalacturonan-II, also inhibited ¹⁴C]leucine incorporationweakly, suggesting that these sugar residues may be an integralrequirement for the biological activity of rhamnogalacturonan-II.The incorporation of ¹⁴C]glutamate and ¹⁴C]histidine, andto a lesser extent ¹⁴C]proline and ¹⁴C]arginine, was alsoinhibited by rhamnogalacturonan-II; the incorporation of ¹⁴C]tyrosineand ¹⁴C]phenylalanine was little affected. This suggests thatrhamnogalacturonan-II exerts its effect by acting on certainmembrane transport systems. Key words: Rhamnogalacturonan-II, inhibition, protein synthesis, amino acid incorporation