PubMed Health⌕ Search
Home/Archive/PubMed

PubMed · 226894

A different genetic code in human mitochondria.

B G Barrell·A T Bankier·J Drouin
View original source ↗Export metadata ↓

Abstract

Comparison of the human mitochrondial DNA sequence of the cytochrome oxidase subunit II gene and the sequence of the corresponding beef heart protein shows that UGA is used as a tryptophan codon and not as a termination codon and suggests that AUA may be a methionine and not an isoleucine codon. The cytochrome oxidase II gene is contiguous at its 5' end with a tRNAAsp gene and there are only 25 bases at its 3' end before a tRNALys gene. These tRNA'S are different from all other known tRNA sequences.

Explore related subjects

Aspartic AcidBase SequenceCodonDNA, MitochondrialElectron Transport Complex IVGenesGenetic CodeHumansIsoleucineLysineMethionineRNA, TransferTryptophanJournal Article

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

B G Barrell, A T Bankier, J Drouin. 1979-11-08. A different genetic code in human mitochondria.. https://doi.org/10.1038/282189a0

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed1992

Structure and dynamics of transmembrane signaling by the Escherichia coli aspartate receptor.

The structure of the cytosolic extension of the first transmembrane region (TM1) of the Escherichia coli aspartate receptor (residues 3, 4, and 5) and conformational changes within that region have been characterized by targeted cross-linking studies and by measurement of the effect of aspartate binding on cross-linking and methylation rates and compared with the periplasmic extension of the same helix. These experiments show that (1) the cytosolic extension of TM1 is helical, with residues 4 and 4' closest together at the dimer interface; (2) the helix is more solvent-exposed at the cytosolic side of the membrane than on the periplasmic side; and (3) aspartate binding enhances the rate of cross-linking at Cys 4, and the resulting cross-linked receptor displays aspartate-induced transmembrane increases in methylation by the cytoplasmic methylase (the CheR protein). We conclude that aspartate induces a conformational change that does not involve large intersubunit movements that lead to an increase in distance between the cytosolic ends of the first membrane-spanning helices; rather, the motion involved is largely contained within individual subunits, possibly resulting in a small movement between positions 4 and 4'.

Aspartic Acid↗
PubMed1992

Site-directed mutagenesis at aspartate and glutamate residues of xylanase from Bacillus pumilus.

To elucidate the reaction mechanism of xylanase, the identification of amino acids essential for its catalysis is of importance. Studies have indicated the possibility that the reaction mechanism of xylanase is similar to that of hen's egg lysozyme, which involves acidic amino acid residues. On the basis of this assumption, together with the three-dimensional structure of Bacillus pumilus xylanase and its amino acid sequence similarity to other xylanases of different origins, three acidic amino acids, namely Asp-21, Glu-93 and Glu-182, were selected for site-directed mutagenesis. The Asp residue was altered to either Ser or Glu, and the Glu residues to Ser or Asp. The purified mutant xylanases D21E, D21S, E93D, E93S, E182D and E182S showed single protein bands of about 26 kDa on SDS/PAGE. C.d. spectra of these mutant enzymes show no effect on the secondary structure of xylanase, except that of D21E, which shows a little variation. Furthermore, mutations of Glu-93 and Glu-182 resulted in a drastic decrease in the specific activity of xylanase as compared with mutation of Asp-21. On the basis of these results we propose that Glu-93 and Glu-182 are the best candidates for the essential catalytic residues of xylanase.

Aspartic Acid↗
PubMed1992

The role of conserved aspartate and serine residues in ligand binding and in function of the 5-HT1A receptor: a site-directed mutation study.

Wild-type and mutant serotonin 1A receptors were transiently expressed in COS-7 cells using the infection-transfection variant of the vaccinia virus/T7 polymerase vector system. The amino acid substitutions in the transmembrane regions, Asp82-->Asn82, Asp116-->Asn116, and Ser198-->Ala198 all resulted in a decrease in affinity for 5-HT by 60-100-fold, without affecting the affinity for the antagonist, pindolol. The binding of agonist to the additional mutant, Thr199-->Ala199, was too weak to be measured, 5-HT induced GTPase activities for all receptors studied. These findings indicate that the residues mutated play an important role in the binding of the agonist and less critical roles in the binding of the antagonist pindolol.

Aspartic Acid↗