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1.
We examined the polymorphism of the lysyl oxidase (LOX) locus, involved in the initiation of muscle collagen cross-linking, in three populations of Atlantic salmon with different
life histories and growth rates and compared it with a closely related species (rainbow trout). Up to four alleles were observed
per individual, probably as a consequence of the tetraploid origin of the salmonid genome. We found high polymorphism in the
LOX locus (16 alleles expressed in total and several low frequency private alleles) in two natural Atlantic salmon populations
and extremely reduced diversity in a farmed population (3 alleles) with low density of collagen crosslinks. We also assessed
the relative role of selection in maintaining LOX genetic variability in Atlantic salmon. Results from several neutrality tests suggest that selection is playing a role in
shaping diversity at the LOX locus. Positive selection was inferred by three different likelihood phylogeny-based methods and one selected site, identified
by all three different methods (PAML, FEL and REL) was located within the “copper-talon” characteristic of LOX proteins. We
suggest that the retention of four alleles in the salmon LOX locus could be related to its multiple functions. 相似文献
2.
The aminoacyl-tRNA synthetases (aaRSs) ensure the fidelity of the translation of the genetic code, covalently attaching appropriate amino acids to the corresponding nucleic acid adaptor molecules-tRNA. The fundamental role of aminoacylation reaction catalysed by aaRSs implies that representatives of the family are thought to be among the earliest proteins to appear. Based on sequence analysis and catalytic domain structure, aaRSs have been partitioned into two classes of 10 enzymes each. However, based on the structural and sequence data only, it will not be easily understood that the present partitioning is not governed by chance. Our findings suggest that organization of amino acid biosynthetic pathways and clustering of aaRSs into different classes are intimately related to one another. A plausible explanation for such a relationship is dictated by early link between aaRSs and amino acids biosynthetic proteins. The aaRSs catalytic cores are highly relevant to the ancient metabolic reactions, namely, amino acids and cofactors biosynthesis. In particular we show that class II aaRSs mostly associated with the primordial amino acids, while class I aaRSs are usually related to amino acids evolved lately. Reasoning from this we propose a possible chronology of genetic code evolution. 相似文献
3.
Summary The chemical and spectroscopic data presented herein show that about 50% of the weight of the termite fungus comb consists
of carbohydrates (⊂40%) and proteinaceous materials (⊂10%). Of the remaining material about 30% appears to be aliphatic in
nature (long-chain and branched alkanoic acids) and 20% aromatic and phenolic. The data on monosaccharide composition indicate
that the fungus comb material, rich in glucose, arabinose and xylose, is predominantly of plant origin. 相似文献
4.
Yu. A. Zolotarev E. M. Dorokhova V. N. Nezavibatko Yu. A. Borisov S. G. Rosenberg G. A. Velikodvorskaia L. V. Neumivakin V. V. Zverlov N. F. Myasoedov 《Amino acids》1995,8(4):353-365
Summary New catalytic reaction between a solid bioorganic compound and activated spillover tritium (ST), based on High-temperature Solid-state Catalytic Isotopic Exchange (HSCIE) was examined. The HSCIE mechanism and determination of the reactivity of hydrogen atoms in amino acids, peptides and proteins was investigated. Quantum mechanical calculations of the reactivity of hydrogen atoms in amino acids in the HSCIE reaction were done. The carbon atom with a greater proton affinity undergoes a greater exchange of hydrogen for tritium in HSCIE. The electrofilic nature of spillover hydrogen in the reaction of HSCIE was revealed. The isotope exchange between ST and the hydrogen of the solid organic compound proceeds with a high degree of configuration retention at the carbon atoms. The HSCIE reaction enables to synthesize tritium labeled proteins with a specific activity of 20–30 mCi/mg and kept biological activity.Presented at the 3rd International Congress on Amino Acids, Peptides and Analogues. Vienna, August, 23–27, 1993 相似文献
5.
Summary. The purpose of the present study was to determine whether the regulation of brain protein synthesis was mediated through changes
in the plasma concentrations of insulin and growth hormone (GH), and whether the concentrations of amino acids in the brain
and plasma regulate the brain protein synthesis when the quantity and quality of dietary protein is manipulated. Two experiments
were done on three groups of aged rats given diets containing 20% casein, 5% casein or 0% casein (Experiment 1), and 20% casein,
20% gluten, or 20% gelatin (Experiment 2) for 1 d (only one 5-h period) after all rats were fed the 20% casein diet for 10
d (only 5-h feeding per day). The aggregation of brain ribosomes, the concentration in plasma GH, and the branched chain amino
acids in the plasma and cerebral cortex declined with a decrease of quantity and quality of dietary protein. The concentration
of plasma insulin did not differ among groups. The results suggest that the ingestion of a higher quantity and quality of
dietary protein increases the concentrations of GH and several amino acids in aged rats, and that the concentrations of GH
and amino acids are at least partly related to the mechanism by which the dietary protein affects brain protein synthesis
in aged rats. 相似文献