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51.
Disulfide structures of human interleukin-6 are similar to those of human granulocyte colony stimulating factor 总被引:2,自引:0,他引:2
C L Clogston T C Boone B C Crandall E A Mendiaz H S Lu 《Archives of biochemistry and biophysics》1989,272(1):144-151
The amino acid sequences of human interleukin-6 and granulocyte colony stimulating factor are approximately 30% homologous in the N-terminal region. The relative positions of four half-cystines in human interleukin-6 (IL-6) match four of the five in human granulocyte colony stimulating factor. Labeling experiments of recombinant interleukin-6 with tritiated iodoacetate confirmed that the molecule forms two intramolecular disulfide bonds and contains no detectable level of free sulfhydryls. By isolation and characterization of tryptic and subtilytic peptides obtained from different proteolytic digestions, the disulfide bonds of the IL-6 molecule were assigned to Cys44-Cys50 and Cys73-Cys83. The two disulfide bridges form two small loops which are separated by 22 amino acids. These structures are similar to those of recombinant granulocyte colony stimulating factor. 相似文献
52.
H R Prasanna K D Nakamura S F Ali M H Lu W Slikker R W Hart 《Biochemical and biophysical research communications》1989,160(1):217-221
The microsomal activation of the potent hepatocarcinogen aflatoxin B1 (AFB1) and the expression of selected protooncogenes were investigated in the livers of rats exposed to delta 9-tetrahydrocannabinol (THC). At equimolar levels of cytochrome P-450, the microsome-mediated binding of AFB1 to DNA was significantly lower (56% of the controls) in preparations from drug exposed rats. Hepatic expression of the c-k-ras protooncogene was 3-fold higher in THC exposed animals. These results suggest the possible occurrence of long lasting residual effects in the rats exposed to THC. 相似文献
53.
The thiol-specific photoactivatable reagent benzophenone iodoacetamide (BPIA) can be selectively incorporated into the most reactive thiol, SH-1, of myosin S1, and upon photolysis, an intramolecular cross-link is formed between SH-1 and the N-terminal 25-kDa region of S1. If a Mg2+-nucleotide is present during photolysis, cross-links can be formed either with the 25-kDa region or with the central 50-kDa region [Lu et al. (1986) Proc. Natl. Acad. Sci. U.S.A. 83, 6392]. Comparison of the peptide maps of cross-linked and un-cross-linked S1 heavy chains indicates that the segment located about 12-16 kDa from the N-terminus of the heavy chain can be cross-linked to SH-1 via BPIA independently of the presence of a nucleotide whereas the segment located 57-60 kDa from the N-terminus can be cross-linked to SH-1 only in the presence of a Mg2+-nucleotide [Sutoh & Lu (1987) Biochemistry 26, 4511]. In this report, S1 was labeled with radioactive BPIA, photolyzed in the absence of nucleotide, and then degraded with proteolytic enzymes. Peptides containing cross-links were isolated by liquid chromatography and subjected to amino acid sequence analyses. The results show that Glu-88 is the major site and Asp-89 and Met-92 are the minor sites involved in cross-linking with SH-1 (Cys-707) via BPIA. These residues are very near the reactive lysine residue (Lys-83) but relatively remote in the primary structure from the putative nucleotide binding region. 相似文献
54.
Cecilia Gotor Eloísa Pajuelo Luís C. Romero Antonio J. Márquez José M. Vega 《Archives of microbiology》1990,153(3):230-234
Polyclonal antiserum specific for ferredoxin-nitrite reductase (EC 1.7.7.1) from the green alga Chlamydomonas reinhardii recognized the nitrite reductase from other green algae, but did not cross-react with the corresponding enzyme from different cyanobacteria or higher plant leaves. An analogous situation was also found for ferredoxin-glutamate synthase (EC 1.4.7.1), using its specific antiserum. Besides, the antibodies raised against C. reinhardii ferredoxin-glutamate synthase were able to inactivate the ferredoxin-dependent activity of nitrite reductase from green algae.These results suggest that there exist similar domains in ferredoxin-nitrite reductases and ferredoxin-glutamate synthases from green algae. In addition, both types of enzymes share common antigenic determinants, probably located at the ferredoxin-binding domain. In spite of their physicochemical resemblances, no apparent antigenic correlation exists between the corresponding enzymes from green algae and those from higher plant leaves or cyanobacteria.Abbreviations Fd
ferredoxin
- GOGAT
glutamate synthase
- MV+
reduced methyl viologen (radical cation)
- NiR
nitrite reductase
- PMSF
phenylmethylsulphonyl fluoride
- SDS
sodium dodecyl sulfate 相似文献
55.
The effect of charge of the Fe(II) reagent used to induce DNA strand cleavage reactions in the presence of a source of reducing equivalents is investigated using two oligonucleotide models. The first consists of the two strands dA20 and dT20, and an equimolar complex between them. The second is a short four-arm branched DNA complex composed of four 16-mer strands. In the former case, cleavage of the 1:1 complex by three reagents with different formal charge, Fe(II).EDTA2-, Fe(II).EDDA and Fe2+, is comparable in rate to that of the individual dT20 and the dA20 strands. While the three reagents show similar cleavage rates for the duplex and single stranded molecules, they give distinctive cutting patterns in the DNA tetramer, consistent with the presence of a site of excess negative charge at the branch point. Scission induced by Fe(II).EDTA2- shows lower reactivity at the branch site relative to duplex controls, whereas Fe(II)2+ shows enhanced reactivity. Formally neutral Fe(II).EDDA shows weak loss of cutting reactivity at the branch. The position of attack by Fe(II)2+ in the branched tetramer is shifted with respect to those of Fe(II).EDTA2- or Fe(II).EDDA; a slower migrating species is also detected in the scission of dA20.dT20 duplex by Fe(II) reaction. These results suggest that the Fe(II)2+ reaction proceeds by a different mechanism from the other agents. The difference in cutting profiles induced by the neutral and negatively charged chelated complexes is consistent with a local electrostatic repulsion of a negatively charged source of radicals, not a positively charged one. 相似文献
56.
Metabolism of phospholipids on erythrocyte membranes 总被引:2,自引:0,他引:2
57.
N R Kallenbach M Lu N Vasant Kumar J W Nelson 《Journal of biomolecular structure & dynamics》1990,7(4):973-983
The effect of the distribution of charged residues on stability of alpha helices in isolated peptides and in globular proteins exemplified by myoglobins from 62 different species is discussed. A highly simplified set of rules is used to account for the interaction of charged groups with the dipole of an alpha helix. Only the position and sign of a charge with respect to the center of the helix and its ability to participate in intrahelical salt bridges determine its effect. These rules lead to a linear correlation between the helicity in variant C-peptide helices from RNAse and the extent to which the charge distribution opposes the helix dipole. Of the sample of 496 helices in the myoglobins studied, 456 exhibit arrangements of charges which oppose the effective dipole moment of the helix according to this calculation. A number of variants occur which leave the backbone moment of helices A-D unchanged, or even add to it. However no such variants exist in the sequences of helices E-H. We suggest that the E, F, G and H helices in myoglobins which show the strongest reversal of the helix dipole participate in the structures of early intermediates in folding of the chain. Stable helix structures should be more likely to occur in these isolated sequences also, and introduction of charge alterations in helices E to H should affect the initial refolding rate of mutant myoglobins. 相似文献
58.
In cultures of Streptomyces fradiae on wool as the only source of nutrition inorganic thiosulfate (in amounts up to 0.5 mg of Na2S2O3·5 H2O/ml) was formed as the final product of metabolization of sulfur from cystine of keratin proteins. The presence of thiosulfate was proved by qualitative tests and thin-layer chromatography and estimated quantitatively by spectrophotometry, titrimetry, and capillary isotachophoresis. Metabolization of organic sulfur to thiosulfate excreted into the medium is a process not yet described in microorganisms. 相似文献
59.
The periplasmic location of enzymes A and B of the thiosulphate-oxidizing multienzyme system of Thiobacillus versutus has been further confirmed by differential radiolabelling of periplasmic and cytoplasmic proteins. The stoichiometries of respiration-driven proton translocation in T. versutus were determined using the oxygen pulse and the initial rate methods. A value for the H+/O quotient (number of protons translocated per oxygen atom reduced) of about 2.8 was found for the oxidation of thiosulphate, and of about 2.5 for sulphite. The H+/O quotient for endogenous respiration was about 5.7. The data are shown to be in good agreement with the scheme proposed previously for thiosulphate oxidation by this organism. Proton generation during the oxidation of thiosulphate or sulphite is indicated to occur in the periplasm rather than by pumping across the cytoplasmic membrane. The results also suggest that a H+/O quotient of six occurs during NADH oxidation (from endogenous metabolism measurements) and that the terminal cytochrome oxidase, aa3, does not function as a proton pump.Abbreviations DCCD
dicyclohexyl carbodiimide
- FCCP
carbonyl cyanide p-trifluoromethoxyphenylhydrazone
- HQNO
2-n-heptyl-4-hydroxyquinoline N-oxide
- TMPD
N,N,N,N-tetramethyl-p-phenylenediamine
- IEF
isoelectric focusing
- HIC
hydrophobic interaction chromatography
- EAI
ethyl acetimidate hydrochloride
- IAI
isethionyl acetimidate 相似文献
60.
K Yamakawa S Kamiya S Nishida K Yoshimura H Yu D Y Lu S Nakamura 《Microbiology and immunology》1988,32(6):579-587
Soil specimens obtained from several areas of Japan, which are closely located to or facing the Continental land of China, were examined for the distribution of Clostridium botulinum, especially pertaining to types A and B. A total of 266 specimens of Japan, when cultured, showed no type A or B toxicity, although 30 (11.3%), 4 (1.5%), and 10 (3.8%) of the specimens showed C1, C2, and type E toxicities, respectively. On the contrary, types A and/or B toxicities were shown, by the same method, in 14 of 20 specimens of Shinkiang district, China. The highest number of C. botulinum cells found in one gram of soil specimen was 25 for type A and 10 for type B. 相似文献