Houde M, Sarhan F
Département des Sciences Biologiques, Université du Québec à Montréal, Canada.
J Gen Microbiol. 1990 Mar;136(3):529-33. doi: 10.1099/00221287-136-3-529.
Different fractionation procedures were used to determine the location of vitamin B12 binding sites in Euglena gracilis. Using uptake measurements, cell fractionation, and light and electron microscopy, the cuticle of the cell was found to be the fraction containing the majority of B12 binding sites. The apparent distribution of vitamin binding sites differed according to the cell lysis method used. The cuticle fraction was responsible for the binding of 80% of the vitamin taken up by the cell during both the rapid and the slow phase of uptake. These results suggest that vitamin B12 binding is regulated, in part, at the cuticle level, and support our previous conclusion that the secondary phase of uptake represents the synthesis of new receptor sites and not the unloading of vitamin inside the cell.
采用不同的分级分离程序来确定纤细裸藻中维生素B12结合位点的位置。通过摄取量测定、细胞分级分离以及光学和电子显微镜观察，发现细胞的角质层是含有大部分B12结合位点的级分。维生素结合位点的表观分布因所用的细胞裂解方法而异。在摄取的快速和慢速阶段，角质层级分负责结合细胞摄取的80%的维生素。这些结果表明，维生素B12的结合部分是在角质层水平受到调控的，并且支持我们之前的结论，即摄取的第二阶段代表新受体位点的合成，而不是细胞内维生素的卸载。
