伸展素在黄瓜胞壁中的转化及其与羟脯氨酸和异联酪氨酸的关系

用~(14)C-Pro和~3H_2-Tyr离体暗培养黄瓜子叶,发现细胞质、SECW和RCW中的Hyp/Pro和Idt/Tyr都随时间呈线性增加。这两种比值后两者高于前者,而两种比值增加速度之比在胞质部分最大、RCW中最小。表明在胞质和胞壁中都有Pro羟化和Tyr异联化过程,但羟化作用主要发生在胞质中,异联化主要在RCW中。 理化处理(高渗溶液和CHM)和放射性示踪证明胞质中存在HRGP库;它被分泌到胞壁后,先以离子键与壁结合,后转变为共价键与壁结合的伸展素。

THE TRANSFORMATION OF EXTENSIN IN CUCUMBER CELL WALL AND ITS RELATIONS WITH HYDROXYPROLINE AND ISODITYROSINE

The excised cotyledons of cucumber incubated in dark are fed With ~(14)C-Pro and ~3H_2-3, 5-Tyr. It has been found that the radioactivity incorporated into the cytoplasm, SECW and RCW increase linearly with time of labeling. During the pulse-chase the radioactivity in cytoplasm decreases quickly, while in SECW decreases at first, then increases and in RCW increases continuously. The Hyp/Pro and Idt/Tyr of the three fractions increase with the time of labeling and the chase of radioactivity. The ratios in SECW and RCW are higher than in the cytoplasm but the is highest in the cytoplasm and lowest in RCW. It indicates that both the hydroxylation of proline and the formation of isodityrosine occur in the cytoplasm and cell wall, but the former mainly in the cytoplasm and the later mostly in RCW.In addition to the growth and decline of the relative radioactivity of the cytoplasm, SECW and RCW, during the chase of ~(14)C-Pro and ~3H_2-3, 5-Tyr it has been found that the protein contents lower in the cytoplasm and increase in SECW and RCW after treatment with cycloheximide. However, the plasmolysis almost has no effect on the protein content of cytoplasm, but the protein in SECW reduces gradually and increases in R.CW. It is proved that there is a pool of hydroxyprolinerich glycoprotein in the cytoplasm. After secreted into the cell wall, it binds with cell wall ionically first, then alters to the covalently wall-bound extensin.