Cunningham P R, Weitzmann C J, Nurse K, Masurel R, Van Knippenberg P H, Ofengand J
Roche Institute of Molecular Biology, Roche Research Center, Nutley, NJ 07110.
Biochim Biophys Acta. 1990 Aug 27;1050(1-3):18-26. doi: 10.1016/0167-4781(90)90135-o.
In vitro synthesis of mutant 16S RNA and reconstitution with ribosomal proteins into a mutant 30S ribosome was used to make all possible single base changes at the universally conserved A1518 and A1519 residues. All of the mutant RNAs could be assembled into a ribosomal subunit which sedimented at 30 S and did not lack any of the ribosomal proteins. A series of in vitro tests of protein synthesis ability showed that all of the mutants had some activity. The amount varied according to the assay and mutant, but was never less than 30% and was generally above 50%. Therefore, neither the conserved A1518 nor A1519 residues are essential for ribosome function. The mutant ribosomes could also be methylated by the ksgA methyltransferase to 70-120% of the expected amount. Thus, neither of the A residues is required for methylation of the other, ruling out any obligate order of methylation of A1518 and A1519.
通过体外合成突变型16S RNA并与核糖体蛋白重组形成突变型30S核糖体，对普遍保守的A1518和A1519残基进行所有可能的单碱基改变。所有突变型RNA都能组装成沉降系数为30 S的核糖体亚基，且不缺少任何核糖体蛋白。一系列蛋白质合成能力的体外测试表明，所有突变体都有一定活性。活性量因测定方法和突变体而异，但从不低于30%，通常高于50%。因此，保守的A1518和A1519残基对核糖体功能都不是必需的。突变型核糖体也能被ksgA甲基转移酶甲基化至预期量的70 - 120%。因此，一个A残基的甲基化不需要另一个A残基，排除了A1518和A1519甲基化的任何必然顺序。
