Cianciarullo A M, Beçak W, Soares M J
Laboratório de Genética, Instituto Butantan, São Paulo, Brazil.
Tissue Cell. 1999 Jun;31(3):342-8. doi: 10.1054/tice.1999.0037.
During the past 25 years, several studies have attempted to determine the site of integration of the heme and the four globin chains in vertebrate erythroid cells that is important in the formation of the hemoglobin molecule. Mitochondrion-like organelles or hemosomes were pointed out as responsible for this task. We performed several experiments to investigate this hypothesis. The intracellular distribution of hemoglobin in amphibian erythroid cells was detected by post-embedding immuno-electron microscopy, using a polyclonal anti-human hemoglobin-proteinA-gold complex. Hemoglobin mapping showed an intense labeling in the cell cytoplasm, but none in cytoplasmic structures such as endoplasmic reticulum, mitochondria, mitochondrion-like organelles, Golgi complex, ribosomes or ferruginous inclusions. The mitochondrial fraction obtained according to the protocol described for some authors, showed by ultrastructural examination that this fraction has a heterogeneous content, also composed by microvesicles rich in cytoplasmic hemoglobin, an artifact generated by mechanical action during cell fractionation. Thus, when this fraction is lysed and its content submitted to electrophoresis, hemoglobin bands would be found inevitably, causing false-positive results, erroneously attributed to hemoglobin content of mitochondrion-like organelles. Our data do not confirm the hypothesis that the final hemoglobin biosynthesis occurs inside mitochondrion-like organelles. They suggest that the hemoglobin molecule be assembled in the erythrocyte cytoplasm outside of mitochondria or hemosomes.
在过去25年里，多项研究试图确定血红素和四条珠蛋白链在脊椎动物红细胞中的整合位点，这对血红蛋白分子的形成至关重要。线粒体样细胞器或血质体被指出负责这项任务。我们进行了多项实验来研究这一假设。利用多克隆抗人血红蛋白-蛋白A-金复合物，通过包埋后免疫电子显微镜检测两栖类红细胞中血红蛋白的细胞内分布。血红蛋白定位显示在细胞质中有强烈标记，但在内质网、线粒体、线粒体样细胞器、高尔基体、核糖体或含铁包涵体等细胞质结构中没有标记。根据一些作者描述的方案获得的线粒体部分，通过超微结构检查表明该部分内容物不均一，还由富含细胞质血红蛋白的微泡组成，这是细胞分级分离过程中机械作用产生的假象。因此，当该部分被裂解并将其内容物进行电泳时，不可避免地会发现血红蛋白条带，从而导致假阳性结果，错误地归因于线粒体样细胞器的血红蛋白含量。我们的数据不支持最终血红蛋白生物合成发生在线粒体样细胞器内的假设。它们表明血红蛋白分子是在线粒体或血质体之外的红细胞细胞质中组装的。
