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The initiator protein Cdc6 (Cdc18 in fission yeast) plays an essential role in the initiation of eukaryotic DNA replication. In yeast the protein is expressed before initiation of DNA replication and is thought to be essential for loading of the helicase onto origin DNA. The biochemical properties of the protein, however, are largely unknown. Using three archaeal homologues of Cdc6, it was found that the proteins are autophosphorylated on Ser residues. The winged-helix domain at the C terminus of Cdc6 interacts with DNA, which apparently regulates the autophosphorylation reaction. Yeast Cdc18 was also found to autophosphorylate, suggesting that this function of Cdc6 may play a widely conserved and essential role in replication initiation.  相似文献   
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Structural genomics (SG) initiatives are currently attempting to achieve the high-throughput determination of protein structures on a genome-wide scale. Here we analyze the SG target data that have been publicly released over a period of 16 months to assess the potential of the SG initiatives. We use statistical techniques most commonly applied in epidemiology to describe the dynamics of targets through the experimental SG pipeline. There is no clear bottleneck among the key stages of cloning, expression, purification and crystallization. An SG target will progress through each of these steps with a probability of approximately 45%. Around 80% of targets with diffraction data will yield a crystal structure, and 20% of targets with HSQC spectra will yield an NMR structure. We also find the overlaps among SG targets: 61% of SG protein sequences share at least 30% sequence identity with one or more other SG targets. There is no significant difference in average structure quality among SG structures and other structures in the PDB determined by "traditional" methods, but on average SG structures are deposited to the PDB twice as quickly after X-ray data collection.  相似文献   
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Haas NB  Grabowski JM  North J  Moran JV  Kazazian HH  Burch JB 《Gene》2001,265(1-2):175-183
CR1 elements and CR1-related (CR1-like) elements are a novel family of non-LTR retrotransposons that are found in all vertebrates (reptilia, amphibia, fish, and mammals), whereas more distantly related elements are found in several invertebrate species. CR1 elements have several features that distinguish them from other non-LTR retrotransposons. Most notably, their 3' termini lack a polyadenylic acid (poly A) tail and instead contain 2-4 copies of a unique 8 bp repeat. CR1 elements are present at approximately 100,000 copies in the chicken genome. The vast majority of these elements are severely 5' truncated and mutated; however, six subfamilies (CR1-A through CR1-F) are resolved by sequence comparisons. One of these subfamilies (i.e. CR1-B) previously was analyzed in detail. In the present study, we identified several full-length elements from the CR1-F subfamily. Although regions within the open reading frames and 3' untranslated regions of CR1-F and CR1-B elements are well conserved, their respective 5' untranslated regions are unrelated. Thus, our results suggest that new CR1 subfamilies form when elements with intact open reading frames acquire new 5' UTRs, which could, in principle, function as promoters.  相似文献   
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Normative data on the in vivo size of the human brain and its major anatomically defined subdivisions are not readily available. In this study, high-resolution magnetic resonance imaging was used to measure regional brain volumes in 46 normal, right-handed adults (23 men, 23 women) between the ages of 22-49 years. Parcellation of the brain was based on neuroanatomical landmarks. The following brain regions were measured: the cerebral hemispheres, frontal lobe, temporal lobe, parietal lobe, occipital lobe, cingulate gyrus, insula, cerebellum, corpus callosum, and lateral ventricles. Males tend to be significantly larger than females, for the whole brain and for nearly all of its major subdivisions, including the corpus callosum. However, the proportional sizes of regions relative to total volume of the hemisphere are remarkably similar in males and females. Variation in size of region is always greater than variation in proportional representation. Asymmetries in brain regions are not profound, with the exception of the cingulate gyrus, which is larger in the left hemisphere. Brain regions are highly correlated in size, with the exception of the lateral ventricles. After controlling for hemisphere size, the volumes of the frontal and parietal lobes are significantly negatively correlated. The occipital lobe tends to be less sexually dimorphic than other major lobes, and less correlated with other brain regions for volume. These results have implications for understanding whether or not certain sectors of the brain have shown relative expansion over the course of hominid and hominoid evolution.  相似文献   
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Mice with null mutations for metallothionein genes MT-1 and MT-2 were used to study the role that metallothionein plays in protecting cellular targets in vivo from oxidative stress. Wild-type (MT(+/+)) and MT-null (MT(-/-)) mice were treated with either saline or zinc and exposed to two types of oxidative stress: gamma-irradiation or 2-nitropropane. There was no alteration in the antioxidant defense system (superoxide dismutase, catalase, or glutathione peroxidase and glutathione levels) to compensate for the lack of the metallothionein in the MT(-/-) mice. The amount of oxidative damage to liver DNA, lipids, and proteins were similar for the MT(-/-) and MT(+/+) mice even though the levels of metallothionein in the livers of the saline- or zinc-pretreated MT(+/+) mice were 5- to 100-fold greater than found in the MT(-/-) mice. To determine if metallothionein can protect mice from the lethal effects of ionizing radiation, the mean survivals of MT(-/-) and MT(+/+) mice exposed to whole body gamma-irradiation were measured and found to be similar. However, the mean survival increased significantly after zinc pretreatment for both the MT(-/-) and MT(+/+) mice. These results demonstrate that tissue levels of metallothionein do not protect mice in vivo against oxidative stress.  相似文献   
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The Porphyridium cruentum light harvesting complex (LHC) binds Chl a, zeaxanthin and -carotene and comprises at least 6 polypeptides of a multigene family. We describe the first in vitro reconstitution of a red algal light-harvesting protein (LHCaR1) with Chl a/carotenoid extracts from P. cruentum. The reconstituted pigment complex (rLHCaR1) is spectrally similar to the native LHC I, with an absorption maximum at 670 nm, a 77 K fluorescence emission peak at 677 nm (ex. 440 nm), and similar circular dichroism spectra. Molar ratios of 4.0 zeaxanthin, 0.3 -carotene and 8.2 Chl a per polypeptide for rLHCaR1 are similar to those of the native LHC I complex (3.1 zeaxanthin, 0.5 -carotene, 8.5 Chl a). The binding of 8 Chl a molecules per apoprotein is consistent with 8 putative Chl-binding sites in the predicted transmembrane helices of LHCaR1. Two of the putative Chl a binding sites (helix 2) in LHCaR1 were assigned to Chl b in Chl a/b-binding (CAB) LHC II [Kühlbrandt et al. (1994) Nature 367: 614–21]. This suggests either that discrimination for binding of Chl a or Chl b is not very specific at these sites or that specificity of binding sites evolved separately in CAB proteins. LHCaR1 can be reconstituted with varying ratios of carotenoids, consistent with our previous observation that the carotenoid to Chl ratio is substantially higher in P. cruentum grown under high irradiance. Also notable is that zeaxanthin does not act as an accessory light-harvesting pigment, even though it is highly likely that it occupies the position assigned to lutein in the CAB LHCs.This revised version was published online in October 2005 with corrections to the Cover Date.  相似文献   
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BackgroundA randomized trial of voluntary medical male circumcision (MC) of HIV—infected men reported increased HIV transmission to female partners among men who resumed sexual intercourse prior to wound healing. We conducted a prospective observational study to assess penile HIV shedding after MC.ConclusionPenile HIV shedding is significantly reduced after healing of MC wounds. Lower plasma VL is associated with decreased frequency and quantity of HIV shedding from MC wounds. Starting ART prior to MC should be considered to reduce male-to-female HIV transmission risk. Research is needed to assess the time on ART required to decrease shedding, and the acceptability and feasibility of initiating ART at the time of MC.  相似文献   
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