McQueen-Mason S, Durachko D M, Cosgrove D J
Department of Biology, Pennsylvania State University, University Park 16802, USA.
Plant Cell. 1992 Nov;4(11):1425-33. doi: 10.1105/tpc.4.11.1425.
Plant cell enlargement is regulated by wall relaxation and yielding, which is thought to be catalyzed by elusive "wall-loosening" enzymes. By employing a reconstitution approach, we found that a crude protein extract from the cell walls of growing cucumber seedlings possessed the ability to induce the extension of isolated cell walls. This activity was restricted to the growing region of the stem and could induce the extension of isolated cell walls from various dicot stems and the leaves of amaryllidaceous monocots, but was less effective on grass coleoptile walls. Endogenous and reconstituted wall extension activities showed similar sensitivities to pH, metal ions, thiol reducing agents, proteases, and boiling in methanol or water. Sequential HPLC fractionation of the active wall extract revealed two proteins with molecular masses of 29 and 30 kD associated with the activity. Each protein, by itself, could induce wall extension without detectable hydrolytic breakdown of the wall. These proteins appear to mediate "acid growth" responses of isolated walls and may catalyze plant cell wall extension by a novel biochemical mechanism.
植物细胞的增大受细胞壁松弛和延展的调控，这一过程被认为是由难以捉摸的“细胞壁松弛”酶催化的。通过采用重组方法，我们发现，来自正在生长的黄瓜幼苗细胞壁的粗蛋白提取物具有诱导分离细胞壁伸展的能力。这种活性局限于茎的生长区域，能够诱导来自各种双子叶植物茎以及石蒜科单子叶植物叶片的分离细胞壁伸展，但对禾本科植物胚芽鞘细胞壁的作用较小。内源性和重组细胞壁伸展活性对pH、金属离子、巯基还原剂、蛋白酶以及在甲醇或水中煮沸表现出相似的敏感性。对活性细胞壁提取物进行连续高效液相色谱分级分离，发现两种分子量分别为29 kD和30 kD的蛋白质与该活性相关。每种蛋白质自身即可诱导细胞壁伸展，且不会检测到细胞壁的水解降解。这些蛋白质似乎介导了分离细胞壁的“酸生长”反应，并且可能通过一种新的生化机制催化植物细胞壁伸展。
