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[Functional and evolutionary aspects of the aminoacyl-tRNA synthetases].

A main event in protein bioshynthesis is the esterification of the correct aminoacid to cognate tRNA catalized by the aminoacyl-tRNA synthetases. The central role of this family of enzymes in metabolism is an evidence of their ancient origin. As it is the case in many others molecules involved in protein synthesis, the emergence of the aminoacyl-tRNA synthetases appears to be a problem that is not yet solved in order to understand the origin of the genetic translation. To obtain a comprehensive view of the evolution of the relationship between each one of the twenty aminoacyl-tRNA synthetases from one organism as well as from different sources (eubacteria, archaebacteria and eukaryotes) we review the information collected from the structural and catalytic properties of these enzyme. The results allow us to establish the following relationship between aminoacyl-tRNA synthetases. On one side there is a monofiletic origin for glutamyl, glutamynil and argynil-tRNA synthetases from Escherichia coli and for valyl, leucyl, metionyl, isoleucyl and phenylalanil-tRNA synthetases from eubacterias, archaebacterias and eukaryotes. On the other side there is an evolutionary relationship between aminoacyl-tRNA synthetases of eubacteria and organelles (plastids and mitochondria) and among eukaryotes and archaebacteria.

Amino Acid Sequence↗
PubMed1975

[Molecular evolution].

The molecular evolution is considered in several protein families. It can be studied with the data of an entirely known structure, like in hemoglobin or cytochrome, or of only partial structural data, as for proteases or immunoglobulins. In the case of isozymes the study of physico-chemical and kinetic properties is more indirect. Finally, it is shown that the molecular mechanisms are always the same, happening probably at the same frequency, the differences being due to a variable selection by molecular constraints and adaptation to the environment.

Biological Evolution↗
PubMed1994

[tRNA identity].

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Amino Acyl-tRNA Synthetases↗
PubMed2002

Origins of gene, genetic code, protein and life: comprehensive view of life systems from a GNC-SNS primitive genetic code hypothesis.

We have investigated the origin of genes, the genetic code, proteins and life using six indices (hydropathy, alpha-helix, beta-sheet and beta-turn formabilities, acidic amino acid content and basic amino acid content) necessary for appropriate three-dimensional structure formation of globular proteins. From the analysis of microbial genes, we have concluded that newly-born genes are products of nonstop frames (NSF) on antisense strands of microbial GC-rich genes [GC-NSF(a)] and from SNS repeating sequences [(SNS)n] similar to the GC-NSF(a) (S and N mean G or C and either of four bases, respectively). We have also proposed that the universal genetic code used by most organisms on the earth presently could be derived from a GNC-SNS primitive genetic code. We have further presented the [GADV]-protein world hypothesis of the origin of life as well as a hypothesis of protein production, suggesting that proteins were originally produced by random peptide formation of amino acids restricted in specific amino acid compositions termed as GNC-, SNS- and GC-NSF(a)-0th order structures of proteins. The [GADV]-protein world hypothesis is primarily derived from the GNC-primitive genetic code hypothesis. It is also expected that basic properties of extant genes and proteins could be revealed by considerations based on the scenario with four stages.

Amino Acids↗