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At least 469 records · Page 26Linked to original sources
PubMed1982

Altered genetic code in Paramecium mitochondria: possible evolutionary trends.

The sequence and presumptive structure of a tRNA trp gene from Paramecium tetraaurelia are given. The gene is located 1,500 bp downstream from the 13S rRNA gene, in about the middle of the genome. Paramecium tRNA trp has a completely normal TpsiC loop and stem, however its anticodon (UCA) constitutes an alteration in the "universal" genetic code, similar to those seen in fungal and mammalian mitochondria. Most features of Paramecium tRNA trp resemble other mitochondrial counterparts; however, its sequence is more homologous to the "unaltered" tRNA trp (anticodon CCA) from E. coli. Paramecium mitochondria may resemble a primitive stage of organelle evolution.

Base Sequence↗
PubMed1992

Genetic code and phylogenetic origin of oomycetous mitochondria.

We sequenced the 3'-terminal part of the COX3 gene encoding cytochrome c oxidase subunit 3 from mitochondria of Phytophthora parasitica (phylum Oomycota, kingdom Protoctista). Comparison of the sequence with known COX3 genes revealed that UGG is used as a tryptophan codon in contrast to UGA in the mitochondrial codes of most organisms other than green plants. A very high AT mutation pressure operates on the mitochondrial genome of Phytophthora, as revealed by codon usage and by A+T content of noncoding regions, which seems paradoxical because AT pressure causes tryptophan codon reassignment from UGG to UGA in mitochondria of most species. The genetic code and other data suggest that mitochondria of Oomycota share a direct common ancestor with mitochondria of plants and that mitochondria of the ancestor of Planta and Oomycota were acquired in a second endosymbiotic event, which occurred later than the acquisition of mitochondria by other eukaryotes.

Amino Acid Sequence↗
PubMed1992

Planarian mitochondria. II. The unique genetic code as deduced from cytochrome c oxidase subunit I gene sequences.

The cytochrome c oxidase subunit I (COI) gene sequences from planarian (Dugesia japonica) DNA, most probably of mitochondrial origin, are heterogeneous. Taking advantage of the heterogeneity that occurs primarily in silent sites of the COI DNA sequences, amino acid assignments of several codons have been deduced as nonuniversal: UGA = Trp, AAA = Asp, and AGR (R: A or G) = Ser. In addition, UAA, a stop codon in the universal genetic code, is tentatively assumed to be a tyrosine codon, because three of the sequences examined have UAA at the well-conserved tyrosine site of UAY (Y: U or C) in other planarian sequences as well as in the mitochondria of human, Xenopus, sea urchin, Drosophila, Trypanosoma, and Saccharomyces cerevisiae. AUA would most probably be an isoleucine codon in these mitochondria, whereas it is a methionine codon in the majority of nonplant mitochondria.

Amino Acid Sequence↗
PubMed2006

Absence of association between two insertion/deletion coding genetic polymorphisms of TIM-1 gene and asthma in Chinese Han population.

TIM-1, a member of T-cell immunoglobulin domain and mucin domain (TIM) gene family, was implicated as an asthma susceptibility gene in previous studies. TIM-1 was expressed on CD4(+) T cells after activation and its expression was sustained preferentially in T-helper type 2 (T(H)2) but not in T(H)1 cells, therefore TIM-1 became a good candidate gene for atopic diseases. Recent studies indicated that two insertion/deletion (ins/del) coding genetic polymorphisms in exon 4 of TIM-1 were associated with asthma susceptibility in some but not in all populations. In order to investigate the relationship between TIM-1 genetic polymorphisms and asthma in Chinese Han population, we performed a case-control study for two insertion/deletion polymorphisms in TIM-1 exon 4 (5383_5397ins/del and 5509_5511delCAA) and a single nucleotide polymorphism (SNP) in intron 8 (IVS 8+9 G/A) between a healthy control group of 309 people and an asthma patient group of 352 people recruited from Chinese Han population. The polymorphisms were genotyped and the allele and genotype frequencies were analysed, but none of the three polymorphisms showed association with asthma susceptibility in single-locus association analyses. Linkage disequilibrium (LD) analyses demonstrated that the two insertion/deletion polymorphisms were in strong LD but the haplotypes constructed from these two polymorphisms showed no significant association with asthma. In conclusion, our findings suggest that 5383_5397ins/del, 5509_5511delCAA and SNP IVS 8+9 G/A polymorphisms are not associated with asthma susceptibility in Chinese Han population.

Adult↗
PubMed1997

The cox1 gene from Euglena gracilis: a protist mitochondrial gene without introns and genetic code modifications.

We present the nucleotide sequence of the cox 1 gene encoding subunit 1 of cytochrome c oxidase in Euglena gracilis, the first report on a mitochondrial gene from this protist. Its study reveals that the Euglena mitochondrial genome does not appear as a compact and homogeneous structure and that its A+T content is high (about 76%) whereas this value is less than 50% in nuclear DNA. The Euglena cox1 gene does not exhibit any intron, and an amino-acid alignment of Euglena COX1 with homologous proteins shows that the universal genetic code is used. Comparisons of the genomic and cDNA sequences of Euglena cox1 indicate that the transcript does not undergo RNA editing as found in trypanosomes and in higher plants. The phylogeny obtained with COX1 protein sequences is in agreement with that obtained with nuclear rRNA sequences and places Euglena and Trypanosoma far apart from other eukaryotes. This result strengthens the hypothesis that these protists represent the earliest mitochondrion-containing organisms.

Amino Acid Sequence↗
PubMed2002

Adding L-3-(2-Naphthyl)alanine to the genetic code of E. coli.

An unnatural amino acid, L-3-(2-naphthyl)alanine, has been site-specifically incorporated into proteins in Escherichia coli. An orthogonal aminoacyl-tRNA synthetase was evolved that uniquely aminoacylates the unnatural amino acid onto an orthogonal amber suppressor tRNA, which delivers the acylated amino acid in response to an amber nonsense codon with translational fidelity greater than 99%. This result, together with the in vivo site-specific incorporation of O-methyl-L-tyrosine reported previously, demonstrate that this methodology may be applicable to a host of amino acids. The expansion of the genetic code to include amino acids beyond the common 20 would provide an opportunity to better understand and possibly enhance protein (and perhaps organismal) function.

Alanine↗