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1.
Helmut Krüger Werner Schr?der Klaus Buchner Ferdinand Hucho 《Journal of Protein Chemistry》1990,9(4):467-473
Inhibition of protein kinase C (PKC) by calmodulin is investigated and we describe the localization of inhibitory sequences within the calmodulin molecule. We present evidence that calmodulin inhibits PKC through an inhibition of the activation of PKC associated with lipid membranes: Binding of PKC to lipid vesicles is not affected, but activation is abolished. The potent calmodulin antagonist R24571 (calmidazol) did not affect the inhibition of PKC by calmodulin at concentrations up to 10–5 M. Two tryptic fragments of calmodulin were isolated which inhibited PKC. They were only slightly less potent than intact calmodulin with an IC50 of 6 µ M compared to 1 µ M of intact calmodulin. They were identified as Ser38-Arg74 and His107-Lys148. Each of the inhibiting fragments contains an intact Ca2+-binding domain with complete helix-loop-helix structure (EF hand). Other calmodulin peptides showed only weak inhibitory activity. Both fragments did not stimulate cAMP phosphodiesterase even at concentrations 100-fold higher than the calmodulin concentration needed for maximal stimulation. None of the fragments acted as a calmodulin antagonist. 相似文献
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Buchner DM 《The Western journal of medicine》1988,148(2):198-199
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Dr. Erich Buchner Sigrid Buchner Garrett Crawford William T. Mason Paul M. Salvaterra David B. Sattelle 《Cell and tissue research》1986,246(1):57-62
Summary Using a monoclonal antibody selective for the acetylcholine (ACh)-synthesizing enzyme choline acetyltransferase (ChAT) of Drosophila melanogaster we find ChAT-like immunoreactivity in specific synaptic regions throughout the brain of Drosophila melanogaster apart from the lobes and the peduncle of the mushroom body and most of the first visual neuropile (lamina). Several anatomically well-defined central brain structures exhibit particularly strong binding. Characteristic differential staining patterns are observed for each of the four neuromeres of the optic lobes. Cell bodies appear not to bind this antibody. The prominent features of the distribution of ChAT-like immunoreactivity are paralleled by the distribution of acetylcholine hydrolyzing enzymatic activity as revealed by histochemical staining for acetylcholine esterase (AChE). These results are discussed in comparison with published data on enzyme distribution, choline uptake and ACh receptor binding in the nervous system of Drosophila melanogaster. 相似文献
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Characterization of a quaternary-structured folding intermediate of an antibody Fab-fragment. 总被引:1,自引:1,他引:0 下载免费PDF全文
H. Lilie R. Jaenicke J. Buchner 《Protein science : a publication of the Protein Society》1995,4(5):917-924
Antibody folding is a complex process comprising folding and association reactions. Although it is usually difficult to characterize kinetic folding intermediates, in the case of the antibody Fab fragment, domain-domain interactions lead to a rate-limiting step of folding, thus accumulating folding intermediates at a late step of folding. Here, we analyzed a late folding intermediate of the Fab fragment of the monoclonal antibody MAK 33 from mouse (kappa/IgG1). As a strategy for accumulation of this intermediate we used partial denaturation of the native Fab by guanidinium chloride. This denaturation intermediate, which can be populated to about 90%, is indistinguishable from a late-folding intermediate with respect to denaturation and renaturation kinetics. The spectroscopic analysis reveals a native-like secondary structure of this intermediate with aromatic side chains only slightly more solvent exposed than in the native state. The respective partner domains are weekly associated. From these data we conclude that the intramolecular association of the two chains during folding, with all domains in a native-like structure, follows a two-step mechanism. In this mechanism, presumably hydrophobic interactions are followed by rearrangements leading to the exact complementarity of the contact sites of the respective domains. 相似文献
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Alternatively folded states of an immunoglobulin 总被引:1,自引:0,他引:1
J Buchner M Renner H Lilie H J Hinz R Jaenicke T Kiefhabel R Rudolph 《Biochemistry》1991,30(28):6922-6929
Well-defined, non-native protein structures of low stability have been increasingly observed as intermediates in protein folding or as equilibrium structures populated under specific solvent conditions. These intermediate structures, frequently referred to as molten globule states, are characterized by the presence of secondary structure, a lack of significant tertiary contacts, increased hydrophobicity and partial specific volume as compared to native structures, and low cooperativity in thermal unfolding. The present study demonstrates that under acidic conditions (pH less than 3) the antibody MAK33 can assume a folded stable conformation. This A-state is characterized by a high degree of secondary structure, increased hydrophobicity, a native-like maximum wavelength of fluorescence emission, and a tendency toward slow aggregation. A prominent feature of this low-pH conformation is the stability against denaturant and thermal unfolding that is manifested in highly cooperative reversible phase transitions indicative of the existence of well-defined tertiary contacts. These thermodynamic results are corroborated by the kinetics of folding from the completely unfolded chain to the alternatively folded state at pH 2. The given data suggest that MAK33 at pH 2 adopts a cooperative structure that differs from the native immunoglobulin fold at pH 7. This alternatively folded state exhibits certain characteristics of the molten globule but differs distinctly from it by its extraordinary structural stability that is characteristic for native protein structures. 相似文献
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