Persson B C, Olafsson O, Lundgren H K, Hederstedt L, Björk G R
Department of Microbiology, Umeå University, Sweden.
J Bacteriol. 1998 Jun;180(12):3144-51. doi: 10.1128/JB.180.12.3144-3151.1998.
The modified nucleoside 2-methylthio-N-6-isopentenyl adenosine (ms2i6A) is present in position 37 (adjacent to and 3' of the anticodon) of tRNAs that read codons beginning with U except tRNA(i.v. Ser) in Escherichia coli. In Salmonella typhimurium, 2-methylthio-N-6-(cis-hydroxy)isopentenyl adenosine (ms2io6A; also referred to as 2-methylthio cis-ribozeatin) is found in tRNA, most likely in the species that have ms2i6A in E. coli. Mutants (miaE) of S. typhimurium in which ms2i6A hydroxylation is blocked are unable to grow aerobically on the dicarboxylic acids of the citric acid cycle. Such mutants have normal uptake of dicarboxylic acids and functional enzymes of the citric acid cycle and the aerobic respiratory chain. The ability of S. typhimurium to grow on succinate, fumarate, and malate is dependent on the state of modification in position 37 of those tRNAs normally having ms2io6A37 and is not due to a second cellular function of tRNA (ms2io6A37)hydroxylase, the miaE gene product. We suggest that S. typhimurium senses the hydroxylation status of the isopentenyl group of the tRNA and will grow on succinate, fumarate, or malate only if the isopentenyl group is hydroxylated.
修饰核苷2-甲硫基-N⁶-异戊烯基腺苷（ms²i⁶A）存在于大肠杆菌中除tRNA（i.v. Ser）外，识别以U开头密码子的tRNA的第37位（与反密码子相邻且在其3'端）。在鼠伤寒沙门氏菌中，2-甲硫基-N⁶-（顺式羟基）异戊烯基腺苷（ms²io⁶A；也称为2-甲硫基顺式核糖玉米素）存在于tRNA中，很可能存在于大肠杆菌中具有ms²i⁶A的物种中。鼠伤寒沙门氏菌中ms²i⁶A羟基化受阻的突变体（miaE）无法在柠檬酸循环的二羧酸上进行有氧生长。此类突变体对二羧酸的摄取正常，且柠檬酸循环和有氧呼吸链的酶功能正常。鼠伤寒沙门氏菌在琥珀酸、富马酸和苹果酸上生长的能力取决于那些通常具有ms²io⁶A³⁷的tRNA第37位的修饰状态，而不是由于tRNA（ms²io⁶A³⁷）羟化酶（miaE基因产物）的第二种细胞功能。我们认为，鼠伤寒沙门氏菌感知tRNA异戊烯基的羟基化状态，并且只有当异戊烯基被羟基化时才会在琥珀酸、富马酸或苹果酸上生长。
