Trewavas A
Biological Sciences, University of East Anglia, Norwich, England.
Plant Physiol. 1972 Jan;49(1):47-51. doi: 10.1104/pp.49.1.47.
The control of protein turnover in Lemna minor has been examined using a method described in the previous paper for determining the rate constants of synthesis and degradation of protein. If Lemna is placed on water, there is a reduction in the rate constants of synthesis of protein and an increase (3- to 6-fold) in the rate constant of degradation. The net effect is a loss of protein from the tissue. Omission of nitrate, phosphate, sulfate, magnesium, or calcium results in increases in the rate constant of degradation of protein.An unusual dual effect of benzyladenine on the turnover constants has been observed. Treatment of Lemna grown on sucrose-mineral salts with benzyladenine results in alterations only in the rate constant of synthesis. Treatment of Lemna grown on water with benzyladenine alters only the rate constant of degradation. Abscisic acid on the other hand alters both rate constants of synthesis and degradation of protein together. Inclusion of growth-inhibiting amino acids in the medium results in a reduction in the rate constants of synthesis and increases in the rate constant of degradation of protein. It is concluded that the rate of turnover of protein in Lemna is very dependent on the composition of the growth medium. Conditions which reduce growth rates also reduce the rates of synthesis of protein and increase those of degradation.
利用前文所述的一种用于测定蛋白质合成和降解速率常数的方法，对浮萍（Lemna minor）中蛋白质周转的控制进行了研究。如果将浮萍置于水中，蛋白质合成的速率常数会降低，而降解的速率常数会增加（3至6倍）。其净效应是组织中蛋白质的损失。去除硝酸盐、磷酸盐、硫酸盐、镁或钙会导致蛋白质降解速率常数增加。已观察到苄基腺嘌呤对周转常数有不同寻常的双重作用。用苄基腺嘌呤处理在蔗糖 - 矿质盐培养基上生长的浮萍，只会改变合成的速率常数。用苄基腺嘌呤处理在水中生长的浮萍，只会改变降解的速率常数。另一方面，脱落酸会同时改变蛋白质合成和降解的速率常数。在培养基中加入生长抑制性氨基酸会导致合成速率常数降低，蛋白质降解速率常数增加。得出的结论是，浮萍中蛋白质的周转速率非常依赖于生长培养基的组成。降低生长速率的条件也会降低蛋白质的合成速率并增加其降解速率。
