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1.
2.
J L Markley D H Croll R Krishnamoorthi G Ortiz-Polo W M Westler W C Bogard M Laskowski 《Journal of cellular biochemistry》1986,30(4):291-309
The traditional approach of using homologous sequences to elucidate the role of specific amino acid residues in protein structure and function becomes more meaningful as the number of differences is minimized, with the limit being alteration of a single residue. For small proteins in solution, NMR spectroscopy offers a means of obtaining detailed information about each residue and its response to a given change in the protein sequence. Extraction of this information has been aided by recent progress in spectrometer technology (higher magnetic fields, more sensitive signal detection, more sophisticated computers) and experimental strategies (new NMR pulse sequences including multiple-quantum and two-dimensional NMR methods). The set of avian ovomucoid third domains, which consists of the third domain proper plus a short leader (connecting peptide) and has a maximum of 56 amino acid residues, offers an attractive system for developing experimental methods for investigating sequence-structure and structure-function relationships in proteins. Our NMR results provide examples of sequence effects on pKa' values, average conformation, and internal motion of amino acid side chains. 相似文献
3.
Summary The effect of KNO3 and N2O on the accumulation of CH4, H2 and denitrification products in two North Dakota soils during anaerobic incubation at 30°C was studied by means of gas chromatography. KNO3 and N2O (500 ppm N) reduced the rate of accumulation of CH4 by a Tetonka soil regardless of whether the soil was in an air-dried condition or had been pre-incubated and actively producing CH4 prior to the treatment application. Both KNO3 and N2O completely suppressed H2 accumulation by the remoistened air-dried soil; no H2 either in the presence or absence of added KNO3 or N2O was accumulated by the pre-incubated Tetonka soil subsequent to the treatment application. KNO3 (250 ppm N) reduced the rate of accumulation of CH4 by a Cavour loam during anaerobic incubation. No H2 was accumulated by this soil during anaerobic incubation. At equivalent K+ concentrations, KNO3 suppressed CH4 accumulation by the Tetonka and Cavour soils to a greater extent than did KCl. 相似文献
4.
The organophosphate cholinesterase inhibitor paraoxon produces a dose-dependent necrosis in rat skeletal muscle fibers after a single administration. The pathology, which is initiated at the motor end-plate region, is evident as early as 30 minutes after paraoxon administration and is characterized by dilated mitochondria, expanded sarcoplasmic reticulum, fused and widened subsynaptic folds, and coated cleft vesicles. By 24 hours, a generalized breakdown of muscle fiber architecture is evident with an accompanying infiltration of phagocytes. Electrophysiological studies have shown that paraoxon increases neurotransmitter release and causes spontaneous and impulse-related antidromic nerve activity, both of which can be reduced significantly by reactivation of inhibited acetylcholinesterase (AChE) with pyridine-2-aldoxime methiodide. The severity of the myopathy has been found to be positively correlated to the degree and duration of AChE inhibition. It appears that 2 hours of inhibition, with a critical loss in activity, viz., 85%, is necessary to initiate severe muscle fiber necrosis. Prior nerve transection prevents myopathic development and current data support the hypothesis that the induction of skeletal muscle fiber necrosis is triggered by inhibition of a neurally regulated fraction of AChE. 相似文献
5.
Effects of the rad 2-20, rad 9-4, r1s, and the corresponding wild type RAD alleles in haploid and homozygous diploid Saccharomyces strains on UV induced mutation rates from adenine, lysine and histidine dependence to independence are reported. The UV induced mutation rates were similar for the RAD, r1s, and rad 9-4 haploids, whereas the rad 2-20 mutation causes a marked increase in the UV induced mutation rates. The diploid rad 2-20 strain also exhibits a marked increase in the UV induced mutation rates, whereas the rad 9-4 diploid has reduced mutation rates when compared to the wildtype. The UV induced mutation rates of haploid and diploid RAD strains are almost identical. For the rad 2-20 and rad 9-4 diploids, however, these rates are smaller than in the corresponding haploid strains. Differential effects of the rad genes on the ratio of locus to suppressor mutations were found. The implications of these findings on possible repair processes in yeasts are discussed. 相似文献
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Theresa K. Hodges Kate L. Laskowski Giuseppe L. Squadrito Maria De Luca Jeff Leips 《Evolution; international journal of organic evolution》2013,67(3):749-760
Populations of Drosophila melanogaster face significant mortality risks from parasitoid wasps that use species‐specific strategies to locate and survive in hosts. We tested the hypothesis that parasitoids with different strategies select for alternative host defense characteristics and in doing so contribute to the maintenance of fitness variation and produce trade‐offs among traits. We characterized defense traits of Drosophila when exposed to parasitoids with different host searching behaviors (Aphaereta sp. and Leptopilina boulardi). We used host larvae with different natural alleles of the gene Dopa decarboxylase (Ddc), a gene controlling the production of dopamine and known to influence the immune response against parasitoids. Previous population genetic analyses indicate that our focal alleles are maintained by balancing selection. Genotypes exhibited a trade‐off between the immune response against Aphaereta sp. and the ability to avoid parasitism by L. boulardi. We also identified a trade‐off between the ability to avoid parasitism by L. boulardi and larval competitive ability as indicated by differences in foraging and feeding behavior. Genotypes differed in dopamine levels potentially explaining variation in these traits. Our results highlight the potential role of parasitoid biodiversity on host fitness variation and implicate Ddc as an antagonistic pleiotropic locus influencing larval fitness traits. 相似文献
9.
Rachael Miller Kate L. Laskowski Martina Schiestl Thomas Bugnyar Christine Schwab 《PloS one》2016,11(2)
Consistent individual differences in behaviour, or ‘personality’, are likely to be influenced by development, social context, and species ecology, though few comparative, longitudinal studies exist. Here, we investigated the role of development and social context on personality variation in two identically reared, social corvids: common ravens and carrion crows. We repeatedly presented subjects with a variety of novel food and objects, while alone and in a primarily sibling subgroup, from fledging to sub-adulthood. We predicted that consistent individual differences would emerge later in development, and that conspecific presence would facilitate behavioural similarities. In contrast to our predictions, we found that individuals of both species were highly inconsistent in their behavioural responses throughout the development period. In line with our predictions, though in the ravens only, conspecific presence promoted behavioural similarities as individuals were strongly shaped by their subgroup, and it is likely that these effects were driven by social context rather than relatedness. We discuss these findings in relation to developmental steps and the role of social relations in these species. Overall, our findings highlight that these two species are highly adaptable in their behaviour, and the ravens in particular are strongly influenced by their social environment, which may facilitate cooperation and social learning. 相似文献
10.
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.
相似文献