| 其他摘要 | Aminoacyl-tRNA synthetase (aaRS) is a key enzyme during protein biosynthesis, which can activate and transfer the corresponding amino acids to its cognate tRNA. This process is very important to make gene be accurately translated into protein and keep the stability and variety of the lives. Generally, each aaRS contains a catalytic central domain (CCD) and an anticodon-binding domain (ABD). A lot of studies show that the gene evolutionary mechanisms and modes, aminoacylation routes, and evolutionary mechanisms in structure and function of many aminoacyl-tRNA synthetases (aaRS), are diverse in some bacteria and eukaryotes. Thus, further studies on these diversities will be useful in understanding protein structural and functional evolution. Although the essential mechanism responsible for these diversities is not understood, these diversities suggest that certain aspects of the biological processes between bacteria and eukaryotes require further study. There are two oligomeric types of glycyl-tRNA synthetases (GlyRSs) in genome, the α2β2 tetramer and α2 dimer. Here, we showed that the anticodon-binding domains (ABDs) of dimeric and tetrameric GlyRSs are non-homologous, although their catalytic central domains (CCDs) are homologous. The dimeric GlyRS_ABD is fused to the C-terminal of CCD in α-subunit, but the tetrameric GlyRS_ABD is to the C-terminal in β-subunit during evolution. Generally, one species only contains one oligomeric type of GlyRS, but the both oligomeric GlyRSs with the multiple homologous domains can be observed in Magnetospirillum magnetotacticum genome, nevertheless, these homologous domains are probably from different genomes. The dimeric GlyRS can be observed in bacteria, archaebacteria and eukaryotes, but the tetrameric GlyRS only exists in most bactetia. GlyRS may have undergone a complex process during the evolution from bacteria to eukaryotes. Frequency gene loss and gain events could result in the different distribution of GlyRS. Gene horizontal transfer is a major factor in tetrameric GlyRS evolution. A number of gene horizontal transfers from bacteria led to the tetrameric GlyRS gene can express in plants and become pseudogenes in animals. Usually, the two class aminoacyl-tRNA synthetases (aaRSs) with different structures and catalytic mechanisms, the class I (aaRS-I) and II (aaRS-II), are suggested to be unrelated in evolution. However, the catalytic mechanism of phenylalanyl-tRNA synthetase (PheRS) belonging to the aaRS-II is similar to that of the aaRS-I. The domain evolutionary analyses show that PheRSs in bacteria and archaebacteria/eukaryotes have the striking different structures, which could result in different recognition mechanisms between PheRS and tRNAPhe during evolution from bacteria, archaebacteria to eukaryotes. Sequence analyses indicate that the PheRS domains, including the catalytic central domain (CCD), the anticodon-binding domain (ABD) and other domains, are homologous with some domains of aaRS-I, thus, the PheRS could be related to the both aaRS-II and aaRS-I in evolution. The results suggest that the aaRS-I and aaRS-II are probably from a common ancestor CCD by gene alternative splicing and insertion during evolution, although the various combinations of these domains have resulted in the obviously difference between the aaRS-I and aaRS-II in structure and in catalytic mechanism. |
修改评论