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Query: EC:3.6.3.14 (ATP synthase)
 7,042 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The sequences of the genes for the nine subunits of ATP synthase in the thermophilic cyanobacterium Synechococcus 6716 have been determined. The genes were identified by comparison of the encoded proteins with sequences of ATP synthase subunits in other species, and confirmed for subunits alpha, beta, delta and epsilon, by determining their N-terminal sequences. They are arranged at three separate loci. Six of them are in one cluster in the order a: c: b': b: delta: alpha, and those for the beta and epsilon subunits form a second and separate cluster. The gene for the gamma-subunit is at a third site. As in other bacteria, the gene for subunit a is immediately preceded by a gene coding for a small hydrophobic protein of unknown function, known as uncI in Escherichia coli. The gene orders in Synechococcus 6716 are related to the orders of ATP synthase genes in the plastid genomes of higher plants, and particularly of a red alga and a diatom. The sequences of the subunits are similar to those of chloroplast ATP synthase, the alpha, beta and c subunits being particularly well conserved. Differences in the primary structures of the Synechococcus 6716 and chloroplast gamma subunits probably underlie different mechanisms of activation of ATP synthase. The nucleotide sequences that are presented also contain 12 other open reading frames. One of them encodes a protein sequence related to the E. coli DNA repair enzyme, photolyase, and another codes for a protein that contains internal repeats related to sequences in the myosin heavy chain.
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PMID:Organization and sequences of genes for the subunits of ATP synthase in the thermophilic cyanobacterium Synechococcus 6716. 836 78

Some molecules, particularly aromatics, have high molar extinction coefficients at wavelengths in the damaging ultraviolet radiation region of the spectrum between 200 and 400 nm. Thus, under a UV radiation flux in which these wavelengths are represented, it could be argued that a selection pressure would exist for a UV transparent biochemistry in which they were not represented. This hypothesis is explored using data made available from proteomics, focusing particularly on tryptophan, against which a selection pressure could exist on present-day Earth as a result of its absorbance shoulder at wavelengths greater than 290 nm. The abundance of tryptophan in whole proteomes is lower than expected from the degeneracy of the genetic code. A lower usage of tryptophan is found in the cytochrome c oxidase polypeptide I of UV-exposed organisms compared to nocturnal and subterranean organisms, but not in ATP synthase chain A. Examination of the amino acid composition of photolyase, an enzyme that requires exposure to light to function, shows that the tryptophan abundances exceed those of the total proteome of most organisms and the abundances expected from the degeneracy of the genetic code. This is also true for cytochrome c oxidase, another enzyme that makes extensive use of the electron transfer properties of tryptophan. We suggest that the selection pressure for the use of tryptophan caused, among other factors, by the uses of delocalised pi-electrons that this aromatic provides in active sites and binding motifs outweighs the selection pressure for UV transparency. This trade-off explains the lack of conclusive evidence for a UV transparent selection pressure. We suggest that this trade-off applies to the stacked pi-electrons of DNA. It offers a solution to the long-standing paradox of why the macromolecule responsible for the faithful replication of information has high absorbance in the damaging UV radiation region of the spectrum.
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PMID:On the plausibility of a UV transparent biochemistry. 1222 30