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1.
The kinetics of the change from the carboxy to the deoxy conformation of the mutated hemoglobins mentioned in the title and of normal human adult hemoglobin were determined from measurements of light absorption changes occurring up to 50 microseconds after nanosecond-laser photodissociation of the corresponding CO complexes. The spectral evolution of the mutated hemoglobins was found to be similar in its main features to that of normal hemoglobin. The kinetics could be decomposed into two phases with rates 1.1-1.8 x 10(6) s-1 and 0.17-0.34 x 10(6) s-1 (except Hb St. Mandé which displayed only the faster phase). Study of the mutated subunits of HbJ Mexico (alpha subunit) and Hb H?tel Dieu (beta subunit) showed that they convert exponentially to the stable deoxy state after photodeligation at the same rates as the corresponding subunits of normal Hb: 1.1 x 10(6) s-1 (alpha) and 0.3 x 10(6) s-1 (beta). The results indicate that there is no direct correlation between the kinetics of spectral relaxation in the time range studied and the oxygenation properties for these hemoglobins. However, there is some indication that the kinetics are dependent upon the region of mutation. 相似文献
2.
REINHARD B
SE KARL T. FRIEDHOFF SYLVIA OLBRICH 《The Journal of eukaryotic microbiology》1987,34(1):110-113
Four fallow deer, Cervus dama, became infected with Trypanosoma (Megatrypanum) sp. by oral application of triturated guts from tabanids collected in an area with deer but without any cattle; four control calves remained negative. Upon challenge with triturated guts from tabanids from an area with pastured cattle, the four calves became infected with Trypanosoma (M.) theileri. The prepatent period in deer was five days or less. Haematopota spp. and Tabanus spp. were identified as vectors of the deer trypanosomes. It is concluded that the trypanosomes of C. dama belong to a Megatrypanum species that is not identical with T. theileri. 相似文献
3.
4.
Crystallographic refinement and structure of ribulose-1,5-bisphosphate carboxylase from Rhodospirillum rubrum at 1.7 A resolution 总被引:7,自引:0,他引:7
The amino acid sequence of ribulose-1,5-bisphosphate carboxylase/oxygenase from Rhodospirillum rubrum has been fitted to the electron density maps. The resulting protein model has been refined to a nominal resolution of 1.7 A using the constrained-restrained least-squares refinement program of Sussman and the restrained least-squares refinement program of Hendrickson & Konnert. The crystallographic refinement, based on 76,452 reflections with F greater than sigma (F) in the resolution range 5.5 to 1.7 A resulted in a crystallographic R-factor of 18.0%. The asymmetric unit contains one dimeric ribulose-1,5-biphosphate carboxylase molecule, consisting of 869 amino acid residues and 736 water molecules. The geometry of the refined model is close to ideal, with root-mean-square deviations of 0.018 A in bond lengths and 2.7 degrees in bond angles. Two loop regions, comprising residues 54 to 63 and 324 to 335, and the last ten amino acid residues at the C terminus are disordered in our crystals. The expected trimodal distribution is obtained for the side-chain chi 1-angles with a marked preference for staggered conformation. The hydrogen-bonding pattern in the N-terminal beta-sheet and the parallel sheet in the beta/alpha-barrel is described. A number of hydrogen bonds and salt bridges are involved in domain-domain and subunit-subunit interactions. The subunit-subunit interface in the dimer covers an area of 2800 A2. Considerable deviations from the local 2-fold symmetry are found at both the N terminus (residues 2 to 5) and the C terminus (residues 422 to 457). Furthermore, loop 8 in the beta/alpha-barrel domain has a different conformation in the two subunits. A number of amino acid side-chains have different conformations in the two subunits. Most of these residues are located at the surface of the protein. An analysis of the individual temperature factors indicates a high mobility of the C-terminal region and for some of the loops at the active site. The positions and B-factors for 736 solvent sites have been refined (average B: 45.9 A2). Most of the solvent molecules are bound as clusters to the protein. The active site of the enzyme, especially the environment of the activator Lys191 in the non-activated enzyme is described. Crystallographic refinement at 1.7 A resolution clearly revealed the presence of a cis-proline at the active site. This residue is part of the highly conserved region Lys166-Pro167-Lys168. 相似文献
5.
Refined structure of spinach glycolate oxidase at 2 A resolution 总被引:11,自引:0,他引:11
Y Lindqvist 《Journal of molecular biology》1989,209(1):151-166
The amino acid sequence of glycolate oxidase from spinach has been fitted to an electron density map of 2.0 A nominal resolution and the structure has been refined using the restrained parameter least-squares refinement of Hendrickson and Konnert. A final crystallographic R-factor of 18.9% was obtained for 32,888 independent reflections from 5.5 to 2 A resolution. The geometry of the model, consisting of 350 amino acid residues, the cofactor flavin mononucleotide and 298 solvent molecules, is close to ideal with root-mean-square deviations of 0.015 A in bond lengths and 2.6 degrees in bond angles. The expected trimodal distribution with preference for staggered conformation is obtained for the side-chain chi 1-angles. The core of the subunit is built up from the eight beta-strands in the beta/alpha-barrel. This core consists of two hydrophobic layers. One in the center is made up of residues pointing in from the beta-strands towards the barrel axis and the second, consisting of two segments of residues, pointing out from the beta-strands towards the eight alpha-helices of the barrel and pointing from the helices towards the strands. The hydrogen bond pattern for the beta-strands in the beta/alpha-barrel is described. There are a number of residues with 3(10)-helix conformation, in particular there is one left-handed helix. The ordered solvent molecules are organized mainly in clusters. The average isotropic temperature factor is quite high, 27.1 A2, perhaps a reflection of the high solvent content in the crystal. The octameric glycolate oxidase molecule, which has 422 symmetry, makes strong interactions around the 4-fold axis forming a tight tetramer, but only weak interactions between the two tetramers forming the octamer. 相似文献
6.
Preliminary crystallographic data for transketolase from yeast 总被引:1,自引:0,他引:1
Crystals of the vitamin B1-dependent enzyme transketolase from baker's yeast have been grown from the apo- and the holoform of the enzyme, using PEG as precipitant. The crystals are orthorhombic, space group P2(1)2(1)2(1) with cell constants a = 76.3 A, b = 114.2 A, and c = 163.5 A. The crystals are stable in the x-ray beam and diffract to at least 2.2 A on a conventional x-ray source. The enzyme is a dimer of identical subunits, and a Vm value of 2.2 A/dalton indicates that the asymmetric unit contains a dimer. Rotation function calculations using native data (10-5 A) revealed a local 2-fold rotation axis with phi = 0 degree and omega = 20 degrees. 相似文献
7.
8.
The apple rootstock,A106(Malus sieboldii),had 17 bivalents in pollen mother cells at meiotic metaphase 1,and 17 chromosomes in a haploid pollen cell.Karyotypes were prepared from root-tip cells with 2n=34 chromosomes,Seven out of 82 karyotypes(8.5%) showed one pari of satellites at the end of the short arm of chromosome 3.C-bands were shown on 6 pairs of chromosomes 2,4,6,8,14,and 16 near the telomeric regions of short arms.Probes for three ripening-related genes from Malus x domestica:endopolygalacturonase(EPG,0.6kb),ACC oxidase(1.2kb),and ACC synthase(2kb)were hybridized in situ to metaphase chromosomes of A106.Hybridization sites for the EPG gene were observed on the long arm of chromosome 14 in 15 out of 16 replicate spreads and proximal to the centromere of chromosomes 6 and 11.For the ACC oxidase gene,hylridization sites were observed in the telomeric region of the short arm of chromosomes 5 and 11 in 87% and 81% of 16 spreads respectively,proxiaml to the centromere of chromosome 1 in 81% of the spreads,and on the long arm of chromosome 13 in 50% of the spreads. Physical mapping of three fruit ripening genes in an apple rootstock A106.Twenty five spreads were studied for the ACC synthase gene and hybridization sites were observed in the telomeric region of the short arm of chromosome 12 in 96% of the spreads.chromosomes 9 and 10 in 76% of the spreads,and chromosome 17 in 56% of the spreads. 相似文献
9.
Recombination between satellite phage P4 and its helper P2. I. In vivo and in vitro construction of P4: :P2 hybrid satellite phage 总被引:1,自引:0,他引:1
B H Lindqvist 《Gene》1981,14(4):231-241
P4::P2 hybrid satellite phages which carry a portion (including the P2 head gene Q and the cohesive end) of the left end of the P2 chromosome linked to the essential part of the P4 chromosome have been isolated by in vivo as well as in vitro recombination. These hybrids express gene Q and grow in the presence of a P2 helper even if defective in gene Q. 相似文献
10.
Interleukin-4 downregulates the p70 chain of the IL-2 receptor on peripheral blood mononuclear cells
Data that support a differential regulation of the interleukin-2 receptor (IL-2R) alpha-(p55 or Tac) and beta-chain (p70) expression by IL-4 are presented. Cytofluorometric analysis performed on peripheral blood mononuclear cells, some of which had been nylon wool passed (enriched for T-cells), in the presence or absence of phytohemagglutinin (PHA) or OKT3, demonstrated that IL-4 has a dose-dependent capacity to inhibit beta-chain IL-2R expression, whereas the alpha-chain is nearly unaffected. We could also, as a consequence of the decreased p70 expression, detect a slight increase in the amounts of IL-2 obtained from PHA-stimulated cultures, when IL-4 was present. Further, the proliferative response, especially to IL-2, but also to PHA alone, was depressed in the presence of IL-4. These data thus give further support to the idea that not only the IL-2R complex as such, but also the two individual IL-2R chains, can be independently regulated. 相似文献