The property and function of tubulin-like protein which is integrated in membrane systems of higher plants

用3-吲哚乙酸（IAA）和赤霉素A_3（GA_3）处理小豆切段，发现一种α-微管蛋白亚型在4 h后消失，推测它整合在膜组分中。6-二甲基氨基嘌呤（6-DMAP）不仅阻止了α-微管蛋白亚型的消失，同时也阻止了GA_3对伸长的促进作用。纯化后的质膜含有微管蛋白，经激素处理后，微管蛋白不消失，在2-D PAGE上显示出独特的行为，免疫电镜观察显示微管蛋白整合成特征性的环状结构。环状结构的直径约为30 nm，与末端复合物的直径相似，事实上，在含有环状结构的制备物中，在Ca^<2+>存在下与UDP-葡萄糖孵育，可形成大量的多糖丝状结构。虽然大多数长丝是B-1，3-葡聚糖，但推测用B-1，3-葡聚糖酶处理后保留的少量硬长丝是纤维素。在液泡膜上发现了微管蛋白，经激素处理后微管蛋白消失。推测液泡膜中的微管蛋白与28 KDa蛋白相关，这取决于二价阳离子的存在。

When the segments of azuki bean were incubated with 3-indoleacetic acid (IAA) plus gibberellin A_3 (GA_3), one isoform of a-tubulin, which was speculated to be integrated in membraneous fraction, was found to disappear after 4h.6-Dimethylaminopurine (6-DMAP) prevented not only the disappearance of the ab but also simulataneously prevented the GA_3-induced promotion of elongation.However, purified plasma membrane contained tubulin which did not disappeare after treatment with hormones ans showed unique behavior on 2-D PAGE.Such tubulin was revealed to be integrated in characteristic ring-shaped structures by immunoelectron microscopic observation. The size of the ring-shaped structures was about 30 nm in diameter and resembled to that of terminal complexes.In fact, the formation of abundant filamentous structures of polysaccharide occurred in the preparations which contained ring-shaped structures by the incubation with UDP-glucose in the presence of Ca^<2+>. Although most filaments were b-1,3-glucan, the minor stiff filaments which remained after treatment with b-1,3-glucanase were speculated to be cellulose. Tubulin which disappeare after the treatment with hormone was found in vacuolar membrane. Tubulin in vacuolar membrane was speculated to be associated with 28 KDa protein depending on the presence of divalent cation.