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1.
Relaxin and its structural relationship to insulin 总被引:2,自引:0,他引:2
2.
Read TD Peterson SN Tourasse N Baillie LW Paulsen IT Nelson KE Tettelin H Fouts DE Eisen JA Gill SR Holtzapple EK Okstad OA Helgason E Rilstone J Wu M Kolonay JF Beanan MJ Dodson RJ Brinkac LM Gwinn M DeBoy RT Madpu R Daugherty SC Durkin AS Haft DH Nelson WC Peterson JD Pop M Khouri HM Radune D Benton JL Mahamoud Y Jiang L Hance IR Weidman JF Berry KJ Plaut RD Wolf AM Watkins KL Nierman WC Hazen A Cline R Redmond C Thwaite JE White O Salzberg SL Thomason B Friedlander AM Koehler TM Hanna PC 《Nature》2003,423(6935):81-86
Bacillus anthracis is an endospore-forming bacterium that causes inhalational anthrax. Key virulence genes are found on plasmids (extra-chromosomal, circular, double-stranded DNA molecules) pXO1 (ref. 2) and pXO2 (ref. 3). To identify additional genes that might contribute to virulence, we analysed the complete sequence of the chromosome of B. anthracis Ames (about 5.23 megabases). We found several chromosomally encoded proteins that may contribute to pathogenicity--including haemolysins, phospholipases and iron acquisition functions--and identified numerous surface proteins that might be important targets for vaccines and drugs. Almost all these putative chromosomal virulence and surface proteins have homologues in Bacillus cereus, highlighting the similarity of B. anthracis to near-neighbours that are not associated with anthrax. By performing a comparative genome hybridization of 19 B. cereus and Bacillus thuringiensis strains against a B. anthracis DNA microarray, we confirmed the general similarity of chromosomal genes among this group of close relatives. However, we found that the gene sequences of pXO1 and pXO2 were more variable between strains, suggesting plasmid mobility in the group. The complete sequence of B. anthracis is a step towards a better understanding of anthrax pathogenesis. 相似文献
3.
DNA sequence of both chromosomes of the cholera pathogen Vibrio cholerae 总被引:23,自引:0,他引:23
Heidelberg JF Eisen JA Nelson WC Clayton RA Gwinn ML Dodson RJ Haft DH Hickey EK Peterson JD Umayam L Gill SR Nelson KE Read TD Tettelin H Richardson D Ermolaeva MD Vamathevan J Bass S Qin H Dragoi I Sellers P McDonald L Utterback T Fleishmann RD Nierman WC White O Salzberg SL Smith HO Colwell RR Mekalanos JJ Venter JC Fraser CM 《Nature》2000,406(6795):477-483
4.
Structural alteration of hair cells in the contralateral ear resulting from extracochlear electrical stimulation 总被引:1,自引:0,他引:1
Chronic electrical stimulation of the auditory nerve in patients with profound sensori-neural deafness is becoming increasingly routine. Therefore, it is important to understand more about the long-term consequences of this procedure. Hitherto, structural studies in animals after electrocochlear stimulation have concentrated on the stimulated cochlea. Here we have examined the effects of unilateral extracochlear electrical stimulation on the spiral organ of both the ipsilateral and contralateral ears of the mature guinea pig, and have found alterations in the structure of the outer hair cells and their efferent nerve terminals in the contralateral as well as the ipsilateral cochlea. This is the first evidence for a structural influence of efferent activity on the cochlea. Although the importance of the efferent system, consisting of the crossed and uncrossed olivo-cochlear bundles, is well established in providing central control of the sensory pathways, its exact role in hearing is incompletely understood. However, it is known that the outer hair cells and their efferent innervation are important in their contribution to inner hair cell responses and in modulating the micromechanics of the whole cochlea. These efferent functions now appear to be related to an important part of cochlear morphology, and are also relevant to our understanding of cochlear neurobiology, normal development and the management of hearing disability in both adult and child. 相似文献
5.
A model for interfacial activation in lipases from the structure of a fungal lipase-inhibitor complex 总被引:37,自引:0,他引:37
A M Brzozowski U Derewenda Z S Derewenda G G Dodson D M Lawson J P Turkenburg F Bjorkling B Huge-Jensen S A Patkar L Thim 《Nature》1991,351(6326):491-494
Lipases are hydrolytic enzymes which break down triacylglycerides into free fatty acids and glycerols. They have been classified as serine hydrolases owing to their inhibition by diethyl p-nitrophenyl phosphate. Lipase activity is greatly increased at the lipid-water interface, a phenomenon known as interfacial activation. X-ray analysis has revealed the atomic structures of two triacylglycerol lipases, unrelated in sequence: the human pancreatic lipase (hPL)4, and an enzyme isolated from the fungus Rhizomucor (formerly Mucor) miehei (RmL). In both enzymes the active centres contain structurally analogous Asp-His-Ser triads (characteristic of serine proteinases), which are buried completely beneath a short helical segment, or 'lid'. Here we present the crystal structure (at 3 A resolution) of a complex of R. miehei lipase with n-hexylphosphonate ethyl ester in which the enzyme's active site is exposed by the movement of the helical lid. This movement also increases the nonpolarity of the surface surrounding the catalytic site. We propose that the structure of the enzyme in this complex is equivalent to the activated state generated by the oil-water interface. 相似文献
6.
J Brange U Ribel J F Hansen G Dodson M T Hansen S Havelund S G Melberg F Norris K Norris L Snel 《Nature》1988,333(6174):679-682
The use of insulin as an injected therapeutic agent for the treatment of diabetes has been one of the outstanding successes of modern medicine. The therapy has, however, had its associated problems, not least because injection of insulin does not lead to normal diurnal concentrations of insulin in the blood. This is especially true at meal times when absorption from subcutaneous tissue is too slow to mimic the normal rapid increments of insulin in the blood. In the neutral solutions used for therapy, insulin is mostly assembled as zinc-containing hexamers and this self-association, which under normal physiological circumstances functions to facilitate proinsulin transport, conversion and intracellular storage, may limit the rate of absorption. We now report that it is possible, by single amino-acid substitutions, to make insulins which are essentially monomeric at pharmaceutical concentrations (0.6 mM) and which have largely preserved their biological activity. These monomeric insulins are absorbed two to three times faster after subcutaneous injection than the present rapid-acting insulins. They are therefore capable of giving diabetic patients a more physiological plasma insulin profile at the time of meal consumption. 相似文献
7.
Evidence for lateral gene transfer between Archaea and bacteria from genome sequence of Thermotoga maritima. 总被引:27,自引:0,他引:27
K E Nelson R A Clayton S R Gill M L Gwinn R J Dodson D H Haft E K Hickey J D Peterson W C Nelson K A Ketchum L McDonald T R Utterback J A Malek K D Linher M M Garrett A M Stewart M D Cotton M S Pratt C A Phillips D Richardson J Heidelberg G G Sutton R D Fleischmann J A Eisen O White S L Salzberg H O Smith J C Venter C M Fraser 《Nature》1999,399(6734):323-329
The 1,860,725-base-pair genome of Thermotoga maritima MSB8 contains 1,877 predicted coding regions, 1,014 (54%) of which have functional assignments and 863 (46%) of which are of unknown function. Genome analysis reveals numerous pathways involved in degradation of sugars and plant polysaccharides, and 108 genes that have orthologues only in the genomes of other thermophilic Eubacteria and Archaea. Of the Eubacteria sequenced to date, T. maritima has the highest percentage (24%) of genes that are most similar to archaeal genes. Eighty-one archaeal-like genes are clustered in 15 regions of the T. maritima genome that range in size from 4 to 20 kilobases. Conservation of gene order between T. maritima and Archaea in many of the clustered regions suggests that lateral gene transfer may have occurred between thermophilic Eubacteria and Archaea. 相似文献
8.
Early agricultural development and environmental effects in the Neolithic Longdong basin (eastern Gansu) 总被引:4,自引:0,他引:4
Neolithic agricultural development and environmental effects in the Longdong area were reconstructed using a synthetic approach,
investigating pollen, charcoal, and seed remains for two cultural layer sections and five flotation sites. Results show that
Neolithic agriculture in the Longdong area had a simple organization and was dominated by the production of common millet,
especially in the early and middle Yangshao age. After the late Yangshao age, Neolithic agriculture developed into a more
complex structure, dominated by both common and foxtail millet and the cultivation of rice and soybeans. The production of
foxtail millet gradually increased through the Neolithic period, reaching its highest point during the Qijia culture. Soybeans
were first cultivated during the late Yangshao culture, approximately 5000 cal a BP. Rice production began no later than 4800
cal a BP, and continued to exist in the Qijia culture, approximately 4000 cal a BP. Agricultural production in Neolithic Longdong,
specifically in the “Yuan” area of the loess plateau, developed as a shrub and grass dominated landscape. Vegetation in the
river valleys was partly covered with Picea, Tusga, and Quercus coniferous and broadleaf mixed forests. Agricultural activity during the Neolithic period caused an increase in farmland
on the loess tableland and a decrease in the abundance of shrub and grassland in the Longdong area. When farmlands were abandoned,
vegetation recovered with Hippophae-, Rosaceae-, Ephedra-, and Leguminosae-dominated shrublands and Artemisia-dominated grasslands. 相似文献
9.
Phenol stabilizes more helix in a new symmetrical zinc insulin hexamer 总被引:14,自引:0,他引:14
U Derewenda Z Derewenda E J Dodson G G Dodson C D Reynolds G D Smith C Sparks D Swenson 《Nature》1989,338(6216):594-596
SINCE insulin was first shown by Scott to crystallize in the presence of zinc ions in 1934, a variety of Zn-containing insulin crystals have been grown. The structures of insulin in the related rhombohedral crystals of 2Zn-insulin and 4Zn-insulin have been solved and reveal that the molecule is a hexamer, organized as three dimers, each containing a 2-fold symmetry axis and held together by Zn ions. In 2Zn-insulin the hexamer is nearly symmetrical with the two axial Zn ions and the two molecules of the dimer related closely by a local 2-fold axis. But in 4Zn-insulin the two molecules in the dimer differ remarkably, creating an asymmetric 4Zn-hexamer in which one trimer is essentially equivalent to that in 2Zn-insulin and the other is different by virtue of an additional stretch of N-terminal helix between residues B1 and B8 (refs 6, 7). We report here the structure of a new symmetrical hexamer, in which all six molecules have the B1-B8 helix seen in 4Zn-insulin. Phenol molecules, found bonding specifically to each molecule, evidently stabilize this new helical conformation. 相似文献
10.
Computer simulations at the atomic level have arrived at a stage where they provide realistic modeling of flexibility in proteins
(and the mobility of their associated solvent) that is important in understanding the nature of molecular motions. This can
now be extended to the molecular and atomic motions that are associated with protein mechanisms. Moreover, the derived data
agree reasonably accurately with experimental measurements of several kinetic and thermodynamic parameters. Fundamental insights
emerge on the roles that this intrinsic flexibility plays in the thermodynamic characteristics of macromolecules in solution;
these equip the investigator to probe the consequences of cognate interactions and ligand binding on entropy and enthalpy.
Thus simulations can now provide a powerful tool for investigating protein mechanisms that complements the existing and the
emerging experimental techniques.
Received 29 May 2005; received after revision 23 August 2005; accepted 21 October 2005 相似文献