Redman K L
Department of Biological Sciences, University of Alabama, Tuscaloosa 35487.
Insect Biochem Mol Biol. 1994 Feb;24(2):191-201. doi: 10.1016/0965-1748(94)90085-x.
The only gene in Drosophila melanogaster for a 52 amino acid ribosomal protein (CEP52) is fused to a ubiquitin coding sequence. This study examines expression and proteolytic processing of the encoded fusion protein. Most antibody preparations made against a portion of human CEP52 readily detect the insect protein. The size of the immunoreactive polypeptide indicates that CEP52 is cleaved from ubiquitin and this apparent proteolytic processing was confirmed by amino-terminal sequence analysis of CEP52 isolated by two-dimensional gel electrophoresis. Ribosomes from embryonic, larval and adult Drosophila melanogaster contain equivalent amounts of CEP52 and the protein is associated with the large ribosomal subunit. Stained two-dimensional gels indicate that the quantity of CEP52 associated with ribosomes is similar to that of other ribosomal proteins of corresponding size. A previous investigation had indicated the possibility of intact ubiquitin-CEP52 fusion protein in Dictyostelium discoideum, Saccharomyces cerevisiae and Drosophila melanogaster. One of three antibody preparations used in this study of insect CEP52 reacts with a 40S subunit protein that is the correct size to be the uncleaved fusion protein. However, the putative fusion protein does not react with ubiquitin antibodies and has negligible positive charge at pH5, demonstrating that it is not unprocessed ubiquitin-CEP52.
果蝇中编码一种52个氨基酸的核糖体蛋白（CEP52）的唯一基因与一个泛素编码序列融合。本研究检测了编码的融合蛋白的表达和蛋白水解加工过程。大多数针对人CEP52一部分制备的抗体都能轻易检测到昆虫蛋白。免疫反应性多肽的大小表明CEP52从泛素中被切割下来，通过二维凝胶电泳分离的CEP52的氨基末端序列分析证实了这种明显的蛋白水解加工。来自果蝇胚胎、幼虫和成虫的核糖体含有等量的CEP52，并且该蛋白与核糖体大亚基相关联。染色的二维凝胶表明与核糖体相关的CEP52的量与相应大小的其他核糖体蛋白的量相似。先前的一项研究表明在盘基网柄菌、酿酒酵母和果蝇中存在完整的泛素-CEP52融合蛋白的可能性。本研究中用于检测昆虫CEP52的三种抗体中的一种与一种40S亚基蛋白发生反应，该蛋白的大小恰好是未切割的融合蛋白的大小。然而，推定的融合蛋白不与泛素抗体发生反应，并且在pH5时带正电荷可忽略不计，这表明它不是未加工的泛素-CEP52。
