Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.9.3.1 (cytochrome oxidase)
 8,822 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We describe the isolation and characterization of two previously undescribed genes, TIF1 and TIF2, from Saccharomyces cerevisiae. The protein-encoding sequences of the two genes are highly conserved, resulting in two completely identical proteins, whereas the flanking regions show no obvious homology. The two yeast proteins are highly similar to the translation initiation factor eIF-4A from mouse. Elevated gene dosage of TIF1 or TIF2 results in the suppression of a missense mutation in the mitochondrial oxi2 gene, which codes for subunit III of cytochrome-c oxidase, although the sequence of the Tif protein indicates its cytoplasmic localization. Inactivation of either gene by gene disruption has no effect on cell viability or on mitochondrial functions. However, simultaneous inactivation of both genes is lethal to the cell.
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PMID:An essential yeast protein, encoded by duplicated genes TIF1 and TIF2 and homologous to the mammalian translation initiation factor eIF-4A, can suppress a mitochondrial missense mutation. 264 98

There has a been a resurgence of debate on whether the Pleistocene glaciations inhibited speciation. This study tests a model of Pleistocene speciation, estimating the phylogenetic relationships and divergence times of 10 species of montane grasshoppers, genus Melanoplus, using 1300 bp of the mitochondrial gene cytochrome oxidase I (COI). Based on average pairwise distances (corrected for multiple substitutions using Kimura's two-parameter model), all species appear to have originated within the Pleistocene. Sequence divergences between species are less than 4%, corresponding to divergence times less than 1.7 million years ago. Branching patterns among the species suggest that speciation was associated with more than one glacial-interglacial cycle. A likelihood-ratio test rejected a model of simultaneous species origins, the predicted branching pattern if species arose from the fragmentation of a widespread ancestor. These grasshoppers live in an area that was previously glaciated and, as inhabitants of the northern Rocky Mountain sky islands, underwent latitudinal and probably altitudinal shifts in distribution in response to climatic fluctuations. Given the repeated distributional shifts and range overlap of the taxa, there most likely has been ample opportunity for population mixing. However, despite periodic glacial cycles, with more than 10 major glaciations over the past million years and climatic fluctuations over as short a time scale as 10(3) to 10(4) years, the dynamic history of the Pleistocene did not preclude speciation. Although relationships among some taxa remain unresolved, these grasshopper species, even with their recent origins, exhibit genetic coherence and monophyletic or paraphyletic gene trees. The frequency of glacial cycles suggests that the speciation process must have been extremely rapid. These species of grasshoppers are morphologically very similar, differing primarily in the shape of the male genitalia. These characters are posited to be under sexual selection, may play an important role in reproductive isolation, and are known to diverge rapidly. This suggests the rapidity of evolution of reproductive isolation may determine whether species divergences occurred during the Pleistocene glaciations.
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PMID:Tests of pleistocene speciation in montane grasshoppers (genus Melanoplus) from the sky islands of western North America. 1100

Climate oscillations of the Quaternary drove the repeated expansion and contraction of ecosystems. Alpine organisms were probably isolated in sky island refugia during warm interglacials, such as now, and expanded their range by migrating down-slope during glacial periods. We used population genetic and phylogenetic approaches to infer how paleoclimatic events influenced the distribution of genetic variation in the predominantly alpine butterfly Parnassius smintheus. We sequenced a 789 bp region of cytochrome oxidase I for 385 individuals from 20 locations throughout the Rocky Mountains, ranging from southern Colorado to northern Montana. Analyses revealed at lease two centers of diversity in the northern and southern Rocky Mountains and strong population structure. Nested clade analysis suggested that the species experienced repeated cycles of population expansion and fragmentation. The estimated ages of these events, assuming a molecular clock, corresponded with paleoclimatic data on habitat expansion and contraction over the past 400,000 years. We propose that alpine butterflies persisted in an archipelago of isolated sky islands during interglacials and that populations expanded and became more connected during cold glacial periods. An archipelago model implies that the effects of genetic drift and selection varied among populations, depending on their latitude, area, and local environment. Alpine organisms are sensitive indicators of climate change and their history can be used to predict how high-elevation ecosystems might respond to further climate warming.
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PMID:Historic cycles of fragmentation and expansion in Parnassius smintheus (papilionidae) inferred using mitochondrial DNA. 1505 24