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1.
Litman GW; Rast JP; Shamblott MJ; Haire RN; Hulst M; Roess W; Litman RT; Hinds- Frey KR; Zilch A; Amemiya CT 《Molecular biology and evolution》1993,10(1):60-72
Immunoglobulins are encoded by a large multigene system that undergoes
somatic rearrangement and additional genetic change during the development
of immunoglobulin-producing cells. Inducible antibody and antibody-like
responses are found in all vertebrates. However, immunoglobulin possessing
disulfide-bonded heavy and light chains and domain-type organization has
been described only in representatives of the jawed vertebrates. High
degrees of nucleotide and predicted amino acid sequence identity are
evident when the segmental elements that constitute the immunoglobulin gene
loci in phylogenetically divergent vertebrates are compared. However, the
organization of gene loci and the manner in which the independent elements
recombine (and diversify) vary markedly among different taxa. One striking
pattern of gene organization is the "cluster type" that appears to be
restricted to the chondrichthyes (cartilaginous fishes) and limits
segmental rearrangement to closely linked elements. This type of gene
organization is associated with both heavy- and light-chain gene loci. In
some cases, the clusters are "joined" or "partially joined" in the germ
line, in effect predetermining or partially predetermining, respectively,
the encoded specificities (the assumption being that these are expressed)
of the individual loci. By relating the sequences of transcribed gene
products to their respective germ-line genes, it is evident that, in some
cases, joined-type genes are expressed. This raises a question about the
existence and/or nature of allelic exclusion in these species. The
extensive variation in gene organization found throughout the vertebrate
species may relate directly to the role of intersegmental
(V<==>D<==>J) distances in the commitment of the individual
antibody-producing cell to a particular genetic specificity. Thus, the
evolution of this locus, perhaps more so than that of others, may reflect
the interrelationships between genetic organization and function.
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2.
The nucleotide and deduced amino acid sequences of the encephalomyocarditis viral polyprotein coding region. 总被引:53,自引:11,他引:42 下载免费PDF全文
A C Palmenberg E M Kirby M R Janda N L Drake G M Duke K F Potratz M S Collett 《Nucleic acids research》1984,12(6):2969-2985
The nucleotide sequence of 7200 bases of encephalomyocarditis (EMC) viral RNA, including the complete polyprotein-coding region, was determined. The polyprotein is encoded within a unique translational reading frame, 6870 bases in length. Protein synthesis begins with the sequence Met-Ala-Thr, and ends with the sequence Leu-Phe-Trp, 126 bases from the 3' end of the RNA. Viral capsid and noncapsid proteins were aligned with the deduced amino acid sequence of the polyprotein. The proteolytic processing map follows the standard 4-3-4 picornaviral pattern except for a short leader peptide (8 kd), which precedes the capsid proteins. Identification of the proteolytic cleavage sites showed that EMC viral protease, p22, has cleavage specificity for gln-gly or gln-ser sequences with adjacent proline residues. The cleavage specificity of the host-coded protease(s) includes both tyr-pro and gln-gly sequences. 相似文献
3.
Rogerio Faustino Ribeiro Jr Felipe F. Potratz Brunella M. M. Pavan Ludimila Forechi Filipe Lugon Moulin Lima Jonaina Fiorim Aurelia Araujo Fernandes Dalton Valentim Vassallo Ivanita Stefanon 《PloS one》2013,8(1)
Carvedilol has beneficial effects on cardiac function in patients with heart failure but its effect on ovariectomy-induced myocardial contractile dysfunction remains unclear. Estrogen deficiency induces myocardial contractile dysfunction and increases cardiovascular disease risk in postmenopausal women. Our aim was to investigate whether carvedilol, a beta receptor blocker, would prevent ovariectomy-induced myocardial contractile dysfunction. Female rats (8 weeks old) that underwent bilateral ovariectomy were randomly assigned to receive daily treatment with carvedilol (OVX+CAR, 20 mg/kg), placebo (OVX) and SHAM for 58 days. Left ventricle papillary muscle was mounted for isometric tension recordings. The inotropic response to Ca2+ (0.62 to 3.75 mM) and isoproterenol (Iso 10−8 to 10−2 M) were assessed. Expression of calcium handling proteins was measured by western blot analysis. Carvedilol treatment in the OVX animals: prevented weight gain and slight hypertrophy, restored the reduced positive inotropic responses to Ca2+ and isoproterenol, prevented the reduction in SERCA2a expression, abolished the increase in superoxide anion production, normalized the increase in p22phox expression, and decreased serum angiotensin converting enzyme (ACE) activity. This study demonstrated that myocardial contractile dysfunction and SERCA2a down regulation were prevented by carvedilol treatment. Superoxide anion production and NADPH oxidase seem to be involved in this response. 相似文献
4.
KR Rupesh PL PremKumar Vasanth V Shiva Kumar Seetharaman S Jayachandran 《BMC microbiology》2002,2(1):5-7
Background
Seeds of the legume plant Lathyrus sativus, which is grown in arid and semi arid tropical regions, contain Diamino Propionic acid (DAP). DAP is a neurotoxin, which, when consumed, causes a disease called Lathyrism. Lathryrism may manifest as Neurolathyrism or Osteolathyrism, in which the nervous system, and bone formation respectively, are affected. DAP ammonia lyase is produced by a few microorganisms such as Salmonella typhi, Salmonella typhimurium and Pseudomonas, and is capable of detoxifying DAP. 相似文献5.
6.
ATP-dependent roles of the DEAD-box protein Mss116p in group II intron splicing in vitro and in vivo
Potratz JP Del Campo M Wolf RZ Lambowitz AM Russell R 《Journal of molecular biology》2011,411(3):661-972
The yeast DEAD-box protein Mss116p functions as a general RNA chaperone in splicing mitochondrial group I and group II introns. For most of its functions, Mss116p is thought to use ATP-dependent RNA unwinding to facilitate RNA structural transitions, but it has been suggested to assist in the folding of one group II intron (aI5γ) primarily by stabilizing a folding intermediate. Here we compare three aI5γ constructs: one with long exons, one with short exons, and a ribozyme construct lacking exons. The long exons result in slower splicing, suggesting that they misfold and/or stabilize nonnative intronic structures. Nevertheless, Mss116p acceleration of all three constructs depends on ATP and is inhibited by mutations that compromise RNA unwinding, suggesting similar mechanisms. Results of splicing assays and a new two-stage assay that separates ribozyme folding and catalysis indicate that maximal folding of all three constructs by Mss116p requires ATP-dependent RNA unwinding. ATP-independent activation is appreciable for only a subpopulation of the minimal ribozyme construct and not for constructs containing exons. As expected for a general RNA chaperone, Mss116p can also disrupt the native ribozyme, which can refold after Mss116p removal. Finally, using yeast strains with mitochondrial DNA containing only the single intron aI5γ,? we show that Mss116p mutants promote splicing in vivo to degrees that correlate with their residual ATP-dependent RNA-unwinding activities. Together, our results indicate that, although DEAD-box proteins play multiple roles in RNA folding, the physiological function of Mss116p in aI5γ splicing includes a requirement for ATP-dependent local unfolding, allowing the conversion of nonfunctional RNA structure into functional RNA structure. 相似文献
7.
A mathematical model is proposed which systematically investigates complex calcium oscillations in pancreatic acinar cells. This model is based on calcium-induced calcium release via inositol trisphosphate receptors (IPR) and ryanodine receptors (RyR) and includes calcium modulation of inositol (1,4,5) trisphosphate (IP3) levels through feedback regulation of degradation and production. In our model, the apical and the basal regions are separated by a region containing mitochondria, which is capable of restricting Ca2+ responses to the apical region. We were able to reproduce the observed oscillatory patterns, from baseline spikes to sinusoidal oscillations. The model predicts that calcium-dependent production and degradation of IP3 is a key mechanism for complex calcium oscillations in pancreatic acinar cells. A partial bifurcation analysis is performed which explores the dynamic behaviour of the model in both apical and basal regions. 相似文献
8.
Regeneration and reestablishment of synaptic connections is an important topic in neurobiological research. In the present study, the regeneration of auditory afferents and the accompanying effects in the central nervous system are investigated in nymphs and adults of the bush cricket Tettigonia viridissima L. (Orthoptera: Tettigoniidae). In all animals in which the tympanal nerve is crushed, neuronal tracing shows a regrowth of the afferents into the prothoracic ganglion. This regeneration is seen in both adult and nymphal stages and starts 10–15 days after nerve crushing. Physiological recordings from the leg nerve indicate a recovery of tympanal fibres and a formation of functional connections to interneurones in the same time range. Electrophysiological recordings from the neck connective suggest additional contralateral sprouting of interneurones and the formation of aberrant connections. The regeneration processes of the tympanal nerve in nymphal stages and adults appear to be similar. 相似文献
9.
ISABELLA URRU JOHANNES STÖKL JEANINE LINZ TAMARA KRÜGEL MARCUS C. STENSMYR BILL S. HANSSON 《Biological journal of the Linnean Society. Linnean Society of London》2010,101(4):991-1001
Flowers of the genus Arum are known to attract dung‐breeding flies and beetles through olfactory deceit. In addition to this strategy, the genus has evolved several other pollination mechanisms. The present study aimed to characterize the pollination strategies of the Cretan Arum species by investigating the flowering phenology, thermogeny, inflorescence odours, and the pollinating fauna. The results obtained show that Arum cyrenaicum and Arum concinnatum emit a strong dung smell and exhibit the distinctive features associated with this pollination syndrome. Both species are highly thermogenic, have a similar odour profile and attract small‐bodied Diptera. Although sharing the same habitat, these two plant species are never found growing sympatrically as a result of the early blooming period of A. cyrenaicum. By contrast, Arum creticum and Arum idaeum have evolved a more traditional and mutually beneficial pollination mechanism. The stinking smell has been replaced by a more flower‐like odour that attracts bees (Lasioglossum sp.) and, occasionally, bugs (Dionconotus cruentatus). Although attracting the same pollinator, the main compound present in the odour of A. creticum is different from that of A. idaeum. Principal component analysis (PCA), based on physiologically active components of the flower odours determined by testing on the antenna of the Lasioglossum bee, revealed two different clusters, indicating that pollinators can potentially discriminate between the odours of the two species. A further PCA on the main floral odour volatiles as identified by gas chroatography‐mass spectroscopy from all the Arum species under investigation displayed odour‐based similarities and differences among the species. The PCA‐gas chomotography‐electroantennographic detection active peaks analysis showed that the two species, A. creticum and A. idaeum, form two groups and are clearly separated from A. cyrenaicum and A. concinnatum, which, conversely, cluster together. The evolutionary forces and selective pressures leading to diversification of pollination mechanisms in the Cretan Arum spp. are discussed. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 991–1001. 相似文献
10.
Doering T Holleran WM Potratz A Vielhaber G Elias PM Suzuki K Sandhoff K 《The Journal of biological chemistry》1999,274(16):11038-11045
The epidermal permeability barrier is maintained by extracellular lipid membranes within the interstices of the stratum corneum. Ceramides, the major components of these multilayered membranes, derive in large part from hydrolysis of glucosylceramides mediated by stratum corneum beta-glucocerebrosidase (beta-GlcCerase). Prosaposin (pSAP) is a large precursor protein that is proteolytically cleaved to form four distinct sphingolipid activator proteins, which stimulate enzymatic hydrolysis of sphingolipids, including glucosylceramide. Recently, pSAP has been eliminated in a mouse model using targeted deletion and homologous recombination. In addition to the extracutaneous findings noted previously, our present data indicate that pSAP deficiency in the epidermis has significant consequences including: 1) an accumulation of epidermal glucosylceramides together with below normal levels of ceramides; 2) alterations in lipids that are bound by ester linkages to proteins of the cornified cell envelope; 3) a thickened stratum lucidum with evidence of scaling; and 4) a striking abnormality in lamellar membrane maturation within the interstices of the stratum corneum. Together, these results demonstrate that the production of pSAP, and presumably mature sphingolipid activator protein generation, is required for normal epidermal barrier formation and function. Moreover, detection of significant amounts of covalently bound omega-OH-GlcCer in pSAP-deficient epidermis suggests that deglucosylation to omega-OH-Cer is not a requisite step prior to covalent attachment of lipid to cornified envelope proteins. 相似文献