RHAMNOGALACTURONAN-II - A BIOLOGICALLY-ACTIVE FRAGMENT

Rhamnogalacturonan-II inhibited the uptake of [C-14]leucine and, consequently, the incorporation of [C-15]leucine into acid-precipitable proteins by suspension-cultured tomato cells. Fractionation of rhamnogalacturonan-II showed that the lower molecular components were the most effective. KDO and apiose, both constituents of rhamnogalacturonan-II, also inhibited [C-14]leucine incorporation weakly, suggesting that these sugar residues may be an integral requirement for the biological activity of rhamnogalacturonan-II. The incorporation of [C-14]glutamate and [C-14]histidine, and to a lesser extent [C-14]proline and [C-14]arginine, was also inhibited by rhamnogalacturonan-II; the incorporation of [C-14]tyrosine and [C-14]phenylalanine was little affected. This suggests that rhamnogalacturonan-II exerts its effect by acting on certain membrane transport systems.