概括
曾经被认为是单独存在于真核生物中的I组自我拼接内子,现在在包括蛋白质细菌在内的多种真核细菌中广泛分布. 这一发现挑战了以前关于 prokaryotic 基因组中的内部起源和分布的观念.
科学领域:
- 分子生物学分子生物学
- 基因组学就是基因组学.
- 进化生物学 进化生物学
背景情况:
- 细胞基因结构具有外子和内子,但内子在细菌基因组中不存在,这表明它们是最近的收购.
- 在蓝藻细菌中,一组I内与叶绿体内处于同一个位置,表明它早于内共生体对真核细胞的入侵.
- 线粒体基因组具有丰富的内核,这表明古代内核可能保留在它们的细菌祖先 (蛋白质细菌) 中.
研究的目的:
- 调查eubacteria中自我拼接I组内的更广泛的存在和分布.
- 为了确定内部子是否存在于不同基因和细菌系外的蓝色细菌.
主要方法:
- 细菌基因组的生物信息分析和分子特征.
- 识别和测序自我拼接的I组内.
主要成果:
- 在Agrobacterium tumefaciens (alpha-Proteobacteria) 和Azoarcus sp.中发现了两个小的自我拼接I组内. (贝塔-蛋白质细菌). 这是一种细菌.
- 在tRNA ((Arg) 和tRNA ((Ile) 基因中分别发现了内子,在保存位置.
- 这些发现表明,在细菌群的基因组上,I组内子存在于细菌群中.
结论:
- I组内子不仅仅局限于真核生物或少数特定的细菌系,而且在真核细菌中广泛分布.
- 在各种细菌基因和群体中存在的内子表明它们是古老的元素,可能早于主要细菌类的分歧.
- 这挑战了对内部子作为最近收购的观点,并支持它们的古代进化起源.
相关概念视频
Transfer RNA Synthesis
One of the unique features of tRNA is the presence of modified bases. In some tRNAs, modified bases account for nearly 20% of the total bases in the molecule. Altogether, these unusual bases protect the tRNA from enzymatic degradation by RNases.
Each of these chemical modifications is carried by a specific enzyme, post-transcription. All of these enzymes have unique base and site-specificity. Methylation, the most common chemical modification, is carried by at least nine different enzymes, with...
Each of these chemical modifications is carried by a specific enzyme, post-transcription. All of these enzymes have unique base and site-specificity. Methylation, the most common chemical modification, is carried by at least nine different enzymes, with...
tRNA Activation
Aminoacyl-tRNA synthetases are present in both eukaryotes and bacteria. Though eukaryotes have 20 different aminoacyl-tRNA synthetases to couple to 20 amino acids, many bacteria do not have genes for all of these aminoacyl-tRNA synthetases. Despite this, they still use all 20 amino acids to synthesize their proteins. For instance, some bacteria do not have the gene encoding the enzyme that couples glutamine with its partner tRNA. In these organisms, one enzyme adds glutamic acid to all of the...
Initiation of Translation
Initiating translation is complex because it involves multiple molecules. Initiator tRNA, ribosomal subunits, and eukaryotic initiation factors (eIFs) are all required to assemble on the initiation codon of mRNA. This process consists of several steps that are mediated by different eIFs.
First, the initiator tRNA must be selected from the pool of elongator tRNAs by eukaryotic initiation factor 2 (eIF2). The initiator tRNA (Met-tRNAi) has conserved sequence elements including modified bases at...
First, the initiator tRNA must be selected from the pool of elongator tRNAs by eukaryotic initiation factor 2 (eIF2). The initiator tRNA (Met-tRNAi) has conserved sequence elements including modified bases at...
Transfer RNA Synthesis
One of the unique features of tRNA is the presence of modified bases. In some tRNAs, modified bases account for nearly 20% of the total bases in the molecule. Altogether, these unusual bases protect the tRNA from enzymatic degradation by RNases.
Each of these chemical modifications is carried by a specific enzyme, post-transcription. All of these enzymes have unique base and site-specificity. Methylation, the most common chemical modification, is carried by at least nine different enzymes, with...
Each of these chemical modifications is carried by a specific enzyme, post-transcription. All of these enzymes have unique base and site-specificity. Methylation, the most common chemical modification, is carried by at least nine different enzymes, with...
tRNA Activation
Aminoacyl-tRNA synthetases are present in both eukaryotes and bacteria. Though eukaryotes have 20 different aminoacyl-tRNA synthetases to couple to 20 amino acids, many bacteria do not have genes for all of these aminoacyl-tRNA synthetases. Despite this, they still use all 20 amino acids to synthesize their proteins. For instance, some bacteria do not have the gene encoding the enzyme that couples glutamine with its partner tRNA. In these organisms, one enzyme adds glutamic acid to all of the...
Coordination of Gene Expression Processes in Bacteria
The DNA replication, transcription, and translation processes are intricately coupled in bacteria, allowing efficient gene expression and rapid protein synthesis. While this physical and functional coordination is advantageous, it introduces challenges that bacteria overcome through specific regulatory mechanisms.Coupling of Replication, Transcription, and TranslationThe coupling of replication, transcription, and translation is a hallmark of bacterial gene expression. As the replisome unwinds...


