Translational apparatus

Palchetti I, Mascini M (2005) Electrochemical Adsorption Technique for Immobilization of Single-Stranded Oligonucleotides onto Carbon Screen-Printed Electrodes. 261 27-43 Pascal R, Boiteau L, Commeyras A (2005) From the Prebiotic Synthesis of a-Amino Acids Towards a Primitive Translation Apparatus for the Synthesis of Peptides. 259 69-122 Paulo A, see Santos I (2005) 252 45-84 Perez EM, see Leigh DA (2006) 265 185-208 Perret F, see Coleman AW (2007) 277 31-88 Perron H, see Coleman AW (2007) 277 31-88 Pianowski Z, see Winssinger N (2007) 278 311-342 Piestert F, see Gansauer A (2007) 279 25-52... 

The main method through which these agents regulate the translational apparatus is via changes in the states of phosphorylation of translation factors and related proteins phosphorylation may, for example, alter the intrinsic activity of translation factors or affect their ability to bind other components (other factors, the ribosome, or RNA). 

Sachs, M. S., Wang, Z., Gaba, A., Fang, P., Belk, J., Ganesan, R., Amrani, N., and Jacobson, A. (2002). Toeprint analysis of the positioning of translation apparatus components at initiation and termination codons of fungal mRNAs. Methods 26, 105-114. 

This chapter presents methods and protocols suitable for the identification and characterization of inhibitors of the prokaryotic and/or eukaryotic translational apparatus as a whole or targeting specific, underexploited targets of the bacterial protein synthetic machinery such as translation initiation and amino-acylation. Some of the methods described have been used successfully for the high-throughput screening of libraries of natural or synthetic compounds and make use of model universal mRNAs that can be translated with similar efficiency by cellfree extracts of bacterial, yeast, and HeLa cells. Other methods presented here are suitable for secondary screening tests aimed at identifying a ... 

The activity of the bacterial translational apparatus can be studied in cellfree systems programmed, depending upon the particular experimental need and design, with any of the mRNAs shown in Fig. 12.1 and listed in Table 12.1. The amount of synthesized product can be assessed using either a radioactive test or, when translation is directed by 027IFCp(A), an immunological test (see later). 

This is a secondary test, the purpose of which is to ascertain that translational inhibitors active on the yeast and/or bacterial translational apparatus are harmless for the human protein synthetic machinery. All the considerations made for the yeast translation apply also to this system. 

Pascal R, Boiteau L, Commeyras A (2005) From the Prebiotic Synthesis of a-Amino Acids Towards a Primitive Translation Apparatus for the Synthesis of Peptides. 259 69-122 Paulo A, see Santos I (2005) 252 45-84... 

Components of the translational apparatus and mutations thereof that affect translation termination... 

It has long been known that insulin ( and other hormones and growth factors) can stimulate protein biosynthesis. The signal transduction pathway linking insulin to the translation apparatus was, imtil recently, imclear. However, insight is now being gained into this mechanism (Pause et al, 1994, review Proud and Denton, 1997). 

Many tRNA sequences are known today, both for a given codon at a variety of phylogenic levels and for a given species and many different anticodons. Each such category is interesting13,14 for comparative analysis. Phylogenic analysis shows whether tRNA has retained information from prebiotic times, or this information has been lost in the course of evolution. The comparison of different tRNA molecules in a single species may then lead to a reasonably complete reconstruction of the early forms and allow statements about the early evolution of the translation apparatus. 

During early development, when cell divisions are occurring rapidly, demand for certain products associated with the translation apparatus (ribosomes) increases. Special regulatory mechanisms ensure that these gene products are produced in the required amounts and that they are not overproduced in the more mature organism. 

From the Prebiotic Synthesis of a-Amino Acids Towards a Primitive Translation Apparatus for the Synthesis of Peptides... 

There is a last possibility to circumvent the above-mentioned difficulties it is that life arose from an early symbiosis between amino acid/peptide and nucleotide/RNA chemistries [21-24]. It is consistent with the fact that the translation machinery (ribosome, fRNAs) seems to be one of the oldest components of the cell as a result of the universality of the genetic code. The translation apparatus would then be considered as a remnant of this interaction. Analysis of biochemical pathways have provided indications in favor of a model based on an early ribonucleopeptide world involving the cooperation of oligopeptides and nucleotides in covalently bound conjugates [25,26]. 

Among activated forms of amino acids, mixed anhydrides with inorganic phosphate or phosphate esters require a special discussion because they are universally involved in peptide biosynthesis through the ribosomal and non-ribosomal pathways. These mixed anhydrides have stimulated studies in prebiotic chemistry very early in the history of this field. Amino acyl adenylates 18c have been shown to polymerize in solution [159,160] and in the presence of clays [139]. However, their participation as major activated amino acid species to the prebiotic formation of peptides from amino acids is unlikely for at least two reasons. Firstly, amino acid adenylates that have a significant lifetime in aqueous solution become very unstable as soon as either CO2 or bicarbonate is present at millimolar concentration [137]. Lacey and coworkers [161] were therefore conduced to consider that CO2 was absent in the primitive atmosphere for aminoacyl adenylate to have a sufficient lifetime and then to allow for the emergence of the modern process of amino acid activation and of the translation apparatus. But this proposition is unlikely, as shown by the analysis of geological records in favor of CO2 contents in the atmosphere higher than present levels [128]. It is also in contradiction with most studies of the evolution of the atmosphere of telluric planets [30,32], Secondly, there is no prebiotic pathway available for adenylate formation and ATP proved to be inefficient in this reaction [162]. 

Regarding the origin of life problem, it remains to determine why this process has been selected by evolution whereas nearly no mixed anhydride is present at equilibrium in the absence of enzyme. If we assume the hypothesis that life emerged from a coevolution process involving both amino acid and nucleotide chemistries, it follows that the translation apparatus must have been formed very early. The only possibility that remains to explain the selection of highly unstable intermediates in peptide biosynthesis is to consider... 

Pascal R, Boiteau L, Commeyras A. From the prebiotic synthesis of a-amino acids towards a primitive translation apparatus for the synthesis of peptides. Top Curr Chem 2005 259 69-122. 

A more accurate replication required protein enzymes, but the synthesis of these enzymes required a primitive translation apparatus, and therefore the presence of genes for such an apparatus. The smallest genome that is capable of coding for a replicase and a rudimentary translation apparatus is not known, but it has been estimated that a minimum of ten genes is necessary in order to keep translation errors within tolerable limits. The appearance of a primitive genome presents, however, two contrasting problems. 

---