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91.
D. R. Dean R. A. Setterquist K. E. Brigle D. J. Scott N. F. Laird W. E. Newton 《Molecular microbiology》1990,4(9):1505-1512
Metallocluster extrusion requirements, interspecies MoFe-protein primary sequence comparisons and comparison of the primary sequences of the MoFe-protein subunits with each other have been used to assign potential P-cluster (Fe-S cluster) domains within the MoFe protein. In each alpha-beta unit of the MoFe protein, alpha-subunit domains, which include potential Fe-S cluster ligands Cys-62, His-83, Cys-88 and Cys-154, and beta-subunit domains, which include potential Fe-S cluster ligands Cys-70, His-90, Cys-95 and Cys-153, are proposed to comprise nearly equivalent P-cluster environments located adjacent to each other in the native protein. As an approach to test this model and to probe the functional properties of the P clusters, amino acid residue substitutions were placed at the alpha-subunit Cys-62, His-83, Cys-88 and Cys-154 positions by site-directed mutagenesis of the Azotobacter vinelandii nifD gene. The diazotrophic growth rates, MoFe-protein acetylene-reduction activities, and whole-cell S = 3/2 electron paramagnetic resonance spectra of these mutants were examined. Results of these experiments show that MoFe-protein alpha-subunit residues, Cys-62 and Cys-154, are probably essential for MoFe-protein activity but that His-83 and Cys-88 residues are not. These results indicate either that His-83 and Cys-88 do not provide essential P-cluster ligands or that a new cluster-ligand arrangement is formed in their absence. 相似文献
92.
93.
Hepatic protein kinase C: translocation stimulated by prolactin and partial hepatectomy 总被引:2,自引:0,他引:2
A R Buckley C W Putnam R Evans H E Laird G N Shah D W Montgomery D H Russell 《Life sciences》1987,41(26):2827-2834
Prolactin stimulates a hepatotrophic response similar to that caused by phorbol esters or partial hepatectomy in rats. Since phorbol esters, which activate protein kinase C, mimic prolactin action in liver, the relationship between prolactin administration and subsequent hepatic protein kinase C translocation was assessed. Prolactin administration rapidly stimulated a 4-fold elevation of membrane protein kinase C activity. The effect of prolactin on hepatic protein kinase C was specific for lactogenic hormones but could be duplicated by phorbol esters. Further, an increase in serum prolactin was demonstrated subsequent to partial hepatectomy and preceding hepatic protein kinase C translocation. Therefore, translocation of hepatic protein kinase C appears important for hepatic proliferation in response to prolactin administration and to partial hepatectomy. 相似文献
94.
95.
Abnormalities were detected in the testes of maturing male Atlantic salmon parr from one hatchery. They consisted of a focal necrosis of germ tissue at the time of rapid cell division when normal germ cells were reaching the spermatid stage of development. Some males taken from sea water which had matured previously in fresh water, had fibrous capsules in their testes as remnants of the freshwater lesion but there were no new abnormalities developing in the gonads. The same stock of fish showed other abnormalities and the authors speculate on a possible connection between these changes and the gonad lesion. 相似文献
96.
Modulations in lipid A and phospholipid biosynthesis pathways influence outer membrane protein assembly in Escherichia coli K-12 总被引:3,自引:3,他引:0
The assembly defect of a mutant outer membrane protein, OmpF315, can be corrected by suppressor mutations that lower lipopolysaccharide (LPS) levels and indirectly elevate phospholipid levels. One such assembly suppressor mutation, asmB1 , is an allele of lpxC ( envA ) whose product catalyses the first rate-limiting step in the lipid A (LPS) biosynthesis pathway. Besides reducing LPS levels, asmB1 confers sensitivity to MacConkey medium. A mutation, sabA1 , that reverses the MacConkey sensitivity phenotype of asmB1 maps within fabZ (whose product is needed for phospholipid synthesis from a precursor) is also required for lipid A synthesis. In addition to reversing MacConkey sensitivity, the sabA1 mutation reverses the OmpF315 assembly suppression phenotype of asmB1 . These results show that OmpF315 assembly suppression by asmB1 , which is achieved by lowering LPS levels, can be averted by a subsequent aberration in phospholipid synthesis at a point where the biosynthetic pathways for these two lipid molecules split. OmpF315 assembly suppression can also be achieved in an asmB + background where FabZ expression is increased. The data obtained in this study provide genetic evidence that elevated phospholipid levels and/or phospholipid to LPS ratios are necessary for assembly suppression. 相似文献
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99.
Mitochondrial DNA from Drosophila melanogaster 总被引:9,自引:0,他引:9
100.
Preparative RP-HPLC analysis of a methanol extract of the seeds of Centaurea cyanus afforded four indole alkaloids: moschamine, cis-moschamine, centcyamine and cis-centcyamine, the latter two being new natural products. Structures of these compounds were elucidated by comprehensive spectroscopic analyses. General toxicity of the isolates was determined by Brine Shrimp Lethality bioassay. 相似文献