Newton D T, Creuzenet C, Mangroo D
Guelph-Waterloo Center for Graduate Work in Chemistry and Biochemistry, Department of Chemistry and Biochemistry, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
J Biol Chem. 1999 Aug 6;274(32):22143-6. doi: 10.1074/jbc.274.32.22143.
Formylation of the initiator methionyl-tRNA, catalyzed by methionyl-tRNA formyltransferase, has long been regarded as essential for initiation of protein synthesis in eubacteria. Here, we show that this process is, in fact, dispensable in Pseudomonas aeruginosa. Disruption of the chromosomal methionyl-tRNA formyltransferase gene in P. aeruginosa resulted only in a moderate decrease in the rate of cell growth, whereas in Escherichia coli cell growth was severely impaired. The ability of the P. aeruginosa mutant strain to grow was not due to an additional copy of the methionyl-tRNA formyltransferase gene or to N-acylation of the methionyl moiety by a group other than formyl. These results indicate that P. aeruginosa can carry out formylation-independent initiation of protein synthesis, using the nonformylated methionyl-tRNA. Therefore, the dogma that eubacteria require formylation of the initiator methionyl-tRNA for initiation of protein synthesis may have been an invalid generalization of results obtained with E. coli.
长期以来，甲硫氨酰 - tRNA甲酰基转移酶催化的起始甲硫氨酰 - tRNA的甲酰化作用，一直被认为是真细菌蛋白质合成起始所必需的。在此，我们表明，实际上这一过程在铜绿假单胞菌中是可有可无的。铜绿假单胞菌中染色体甲硫氨酰 - tRNA甲酰基转移酶基因的破坏仅导致细胞生长速率适度下降，而在大肠杆菌中细胞生长则严重受损。铜绿假单胞菌突变株的生长能力并非由于甲硫氨酰 - tRNA甲酰基转移酶基因的额外拷贝，也不是由于除甲酰基以外的其他基团对甲硫氨酰部分进行N - 酰化作用。这些结果表明，铜绿假单胞菌可以利用未甲酰化的甲硫氨酰 - tRNA进行不依赖甲酰化的蛋白质合成起始。因此，关于真细菌需要起始甲硫氨酰 - tRNA甲酰化来进行蛋白质合成起始的教条，可能是对大肠杆菌实验结果的无效概括。
