Cellulose Synthesis on Isolated Tubulin-Containing Granules from Plasma Membranes of Azuki Bean Epicotyls

微管蛋白一直被认为是细胞质微管的主要组成部分，参与植物发育的各种过程。然而，在高等植物的质膜中已经证实存在一种独特的微管蛋白，并且被认为对细胞伸长具有重要作用。在高等植物细胞中，皮层Mts被认为控制纤维素微纤丝的取向，因为Mts通常平行于新沉积的微纤丝排列。然而，皮质MT控制纤维素微纤维取向的机制尚未阐明。据推测，纤维素微纤丝是由与质膜结合的末端复合物组装而成的。在各种细胞质膜的冷冻断裂复制品中观察到了末端复合物，形成直径约25 nm的颗粒。莲座状结构由6个直径为8-9 nm的颗粒组成。高等 ...更多信息 植物细胞，分离和鉴定的终端复合物尚未成功，虽然一些可能的模型的关系的MT和纤维素synthes.In洗涤剂溶解制备的质膜从上胚轴的红豆，微管蛋白被证明是整合在颗粒直径约10 nm。这些颗粒的大小与形成玫瑰花结结构的颗粒的大小相似。利用微管蛋白抗体成功地分离了这些颗粒。SDS-PAGE分析表明，颗粒由33、42和120 kD的蛋白质组成，其中微管蛋白含量最高。用33 kD蛋白的特异性抗体，在体外纤维素的合成被完全抑制，免疫电镜表明，33 kD蛋白是整合在这些颗粒。由于33 kD蛋白质结合13 <32>P标记的UDP-葡萄糖，因此估计该蛋白质是复合物的重要组分。对编码33 kD蛋白的基因进行了克隆，并对其氨基酸序列进行了鉴定。少

Until recently, tubulin was always considered exclusively to be a major constituent of cytoplasmic microtubules, which participatein a wide variety of processes in plant development. However, the presence has been confirmed of a unique tubulin in the plasma membranes of higher plants and was assumed to have an important role for cell elongation. Cortical Mts are considered to control the orientation of cellulose microfibrils in higher plant cells since MTs are often aligned parallel to newly desposited microfibrils. However, the mechanism whereby cortical MTs control the orientation of cellulose microfibrils has not been clarified. It has been postulated that cellulose microfibrils are assembled by terminal complexes in association with the plasma membrane. Terminal complexes have been observed in freeze-fracture replicas of the plasma membranes of various cells, forming rosettes of about 25 nm in diameter. The rosette structure consists of six granules of 8-9 nm in diameter. In higher … More plant cells, the isolation and identification of terminal complexes has not yet been successful, although some possible models for the relation of MTs and cellulose synthase have been presented.In a detergent-solubilized preparation of plasma membranes from epicotyls of azuki bean, tubulin was shown to be integrated in granules of about 10 nm in diameter. The size of these granules was similar to that of the granules that form the rossette structures. The method was developed to isolate these granules using antibodies against tubulin successfully. Asnalysis on SDS-PAGE indicated that the granules consisted of several proteins, 33,42 and 120 kD,respectively, including tubulin as the most abundant constituent. Using specific antibodies against 33 kD protein, in vitro synthesis of cellulose was inhibited entirely and the immunoelectron microscopy indicated that 33 kD protein is integrated in these granules. Since the 33 kD protein binds ^<32>P-labeled UDP-glucose, this protein was estimated to be important constituent of complexes. The cloning of gene coding 33kD protein was performed and the identification of amino acid sequence was also accomplished. Less