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1.
S Ravichandran J Dasgupta C Chakrabarti S Ghosh M Singh J K Dattagupta 《Protein engineering》2001,14(5):349-357
A double-headed chymotrypsin inhibitor, WCI, from winged bean seeds was cloned for structural and biochemical studies. The inhibitor was subjected to two point mutations at a conserved position, Asn14. This residue, known to have a pivotal role in stabilizing the first reactive-site loop (Gln63-Phe68) of the inhibitor, is highly conserved in the sequences of the other members of Kunitz (STI) family as well as in the sequences of Kazal family of serine protease inhibitors. The mutants, N14K and N14D, were subjected to biochemical assay and their characteristics were compared with those of the recombinant inhibitor (rWCI). Crystallographic studies of the recombinant and the mutant proteins are discussed. These studies were primarily aimed at understanding the importance of the protein scaffolding towards the conformational rigidity of the reactive-site loop. Our analysis reveals that, as the Lys14 side chain takes an unusual fold in N14K and the Asp14 side chain in N14D interacts with the loop residues by water-mediated hydrogen bonds, the canonical conformation of the loop has remained effectively intact in both the mutant structures. However, minor alterations such as a 2-fold increase in the inhibitory affinity towards the cognate enzyme were observed. 相似文献
2.
A series of metal carboxylates containing pyridine N-oxide are prepared via one pot synthesis and solid phase synthesis. The structural variations from metal to metal are observed. In the case of reactions of manganese(II) acetate with pyridine N-oxide in the presence of aromatic carboxylic acids, polymeric complexes with bridging aromatic carboxylate as well as bridging pyridine N-oxide are observed. Whereas, the reaction of copper(II) acetate with pyridine N-oxide in the presence of an aromatic carboxylic acid led to mononuclear or binuclear paddle wheel carboxylate complexes with monodentate pyridine N-oxide. Co-crystal of two neutral complexes having composition [Cu2(OBz)4(MeOH)2][Cu2(OBz)4(pyO)2] (where OBz = benzoate, pyO = pyridine N-oxide) each neutral parts have paddle wheel structure. Solid phase reaction of zinc chloride with sodium benzoate prepared in situ and pyridine N-oxide leads to a tetra-nuclear zinc complex. 相似文献
3.
Background
Meiotic prophase is a critical stage in sexual reproduction. Aberrant chromosome recombination during this stage is a leading cause of human miscarriages and birth defects. However, due to the experimental intractability of mammalian gonads, only a very limited number of meiotic genes have been characterized. Here we aim to identify novel meiotic genes important in human reproduction through computational mining of cross-species and cross-sex time-series expression data from budding yeast, mouse postnatal testis, mouse embryonic ovary, and human fetal ovary. 相似文献4.
Primer-dependent synthesis of covalently linked dimeric RNA molecules by poliovirus replicase. 总被引:12,自引:10,他引:2 下载免费PDF全文
Poliovirus-specific RNA-dependent RNA polymerase (replicase, 3Dpol) was purified from HeLa cells infected with poliovirus. The purified enzyme preparation contained two proteins of apparent molecular weights 63,000 and 35,000. The 63,000-Mr polypeptide was virus-specific RNA-dependent RNA polymerase, and the 35,000-Mr polypeptide was of host origin. Both polypeptides copurified through five column chromatographic steps. The purified enzyme preparation catalyzed synthesis of covalently linked dimeric RNA products from a poliovirion RNA template. This reaction was absolutely dependent on added oligo(U) primer, and the dimeric product appeared to be made of both plus- and minus-strand RNA molecules. Experiments with 5' [32P]oligo(U) primer and all four unlabeled nucleotides suggest that the viral replicase elongates the primer, copying the poliovirion RNA template (plus strand), and the newly synthesized minus strand snaps back on itself to generate a template-primer structure which is elongated by the replicase to form covalently linked dimeric RNA molecules. Kinetic studies showed that a partially purified preparation of poliovirus replicase contains a nuclease which can cleave the covalently linked dimeric RNA molecules, generating template-length RNA products. 相似文献
5.
6.
The 7 ns 436 nm pulses of an H2-shifted YAG laser have been used to photolyze the CO adduct of cytochrome-c peroxidase and produce the resonance Raman spectrum of the photoproduct. A 3 cm-1 downshift, relative to the spectrum of reduced enzyme, was observed for the porphyrin C-N breathing mode, v4. The downshift diminishes with decreasing CO /protein ratio, implying, in conjunction with a recent study of CO binding, that the unrelaxed heme is associated with adduct having a tilted, H-bonded FeCO unit. The downshift is eliminated when the phosphate buffer concentration is increased from 0.01 to 0.1 M. It is proposed that the heme relaxation under study involves a transition between two conformations, B and A, differing in the disposition of the distal residues, and having different v4 frequencies for unligated Fe(II) heme. Conformation B allows H-bonding to bound CO, and is favored at high CO and phosphate concentrations, while conformation A, which is unfavorable to CO H-bonding, is favored at low CO and phosphate concentrations. The recently reported absence of unrelaxed frequencies in the 7 ns photo-product of the CO adduct of horseradish peroxidase has been confirmed, and is attributed to lower stability for conformation B and a smaller A - B v4 difference. 相似文献
7.
Shyamali Mukherjee Mihir Nag Tultul Nayyar Indrani Maitra Parul Chakrabarti Pramod R. Dasgupta 《Journal of biosciences》1986,10(3):311-317
The effect of estradiol-17β and progesterone given separately as well as in combination on the rate of hydrogen peroxide formation
and lipid peroxidation in the uteri of ovariectomized rats was studied. Estradiol in 3μg dose per day per animal elicited maximum stimulatory response and progesterone (100μg), on the other hand, was without any such effect. However, progesterone given along with estradiol completely prevented the
effect due to the latter. In the same way, vitamin E, a well known antioxidant was found to be extremelv effective in protecting
the uterus from the highly peroxidative action of estradiol-17β. 相似文献
8.
9.
Structural characterization of cytochrome c peroxidase by resonance Raman scattering 总被引:1,自引:0,他引:1
Resonance Raman scattering studies are reported on freshly prepared and aged ferric, ligand-free ferrous, and CO-bound ferrous cytochrome c peroxidase. The ferric form of the fresh enzyme has a heme which is penta-coordinate high spin, independent of buffer over the pH range 4.3-7, as determined by well established Raman marker lines. The aged enzyme displays a mixture of spin and coordination states, but it can be stabilized in the penta-coordinate high spin form in the presence of phosphate. These results can be accounted for by considering the size of the channel (6 A wide, 11 A long) between the distal side of the heme and the outer surface of the protein. A phosphate ion may be accommodated in this channel resulting in the stabilization of the distal heme pocket. The ferrous cytochrome c peroxidase in both the ligand-free and CO-bound states has an acidic and an alkaline form. The acidic form has the characteristic spectral features of peroxidases: a high frequency iron-histidine stretching mode (248 cm-1), a high frequency Fe-CO stretching mode (537 cm-1), and a low frequency C-O stretching mode (1922 cm-1). At alkaline pH these frequencies become similar to those of hemoglobin and myoglobin, with the corresponding modes located at 227, 510, and 1948 cm-1, respectively. We attribute the acid/alkaline transition in the ferrous forms of cytochrome c peroxidase to a rearrangement mainly of the proximal side of the heme, culminating in a change of steric interactions between the proximal histidine and the heme or of the hydrogen bonding network involving the proximal histidine. The new data presented here reconcile many inconsistencies reported in the past. 相似文献
10.
Multiple transcriptional regulatory domains in the human immunodeficiency virus type 1 long terminal repeat are involved in basal and E1A/E1B-induced promoter activity 总被引:10,自引:7,他引:3 下载免费PDF全文
S Kliewer J Garcia L Pearson E Soultanakis A Dasgupta R Gaynor 《Journal of virology》1989,63(11):4616-4625