Green J R, Northcote D H
J Cell Sci. 1979 Dec;40:235-44. doi: 10.1242/jcs.40.1.235.
There are two fucosyl transferase activities present within the endomembranes of the cells of maize root-tips. One transfers fucose to polyprenyl phosphate and occurs in the endoplasmic reticulum, the second transfers fucose probably to polysaccharide or glycoprotein. In order to show an association of this second fucosyl transferase activity with the endoplasmic reticulum as well as the Golgi apparatus, a method of fractionating the membranes in a discontinuous sucrose gradient was used. Membranes were prepared in the presence of Mg2+, which maintained the attachment of ribosomes to the endoplasmic reticulum, and also in the presence of EDTA, which removed most of the ribosome complex. This caused a shift in density of these membranes. Two types of experiments were carried out; either maize roots were incubated in L-[1-3H]fucose and then membranes prepared and the amount of polymer synthesized in vivo determined or isolated membranes were incubated with GDP-L-[U-14C]fucose in vitro and the amount of polymer synthesized was found. The results showed that the Golgi apparatus had the highest amount of this fucosyl transferase activity, but there was a significant amount of activity associated with the endoplasmic reticulum and the latter was shifted in the sucrose gradient depending on the conditions used.
玉米根尖细胞内膜中存在两种岩藻糖基转移酶活性。一种将岩藻糖转移至聚异戊二烯磷酸，存在于内质网中；另一种可能将岩藻糖转移至多糖或糖蛋白。为了显示这种第二种岩藻糖基转移酶活性与内质网以及高尔基体的关联，采用了一种在不连续蔗糖梯度中分离膜的方法。在存在Mg2+（其维持核糖体与内质网的附着）以及存在EDTA（其去除大部分核糖体复合物）的情况下制备膜。这导致这些膜的密度发生变化。进行了两类实验：要么将玉米根在L-[1-3H]岩藻糖中孵育，然后制备膜并测定体内合成聚合物的量，要么将分离的膜在体外与GDP-L-[U-14C]岩藻糖孵育并测定合成聚合物的量。结果表明，高尔基体具有这种岩藻糖基转移酶活性的最高量，但内质网也有相当量的活性，并且内质网在蔗糖梯度中的位置会根据所用条件而发生变化。
