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1.
2.
Highly oriented samples of lipid and gramicidin A' (8:1 molar ratio) have been prepared with the samples extensively hydrated (approximately 70% water v/w). These preparations have been shown to be completely in a bilayer phase with a transition temperature of 28 degrees C, and evidence is presented indicating that the gramicidin is in the channel conformation. An estimate of the disorder in the alignment of the bilayers parallel with the glass plates used to align the bilayers can be made from the asymmetry of the nuclear magnetic resonances (NMR). Such an analysis indicates a maximal range of disorder of +/- 3 degrees. Uniformly 15N-labeled gramicidin has been biosynthesized by Bacillus brevis grown in a media containing 15N-labeled Escherichia coli cells as the only nitrogen source. When prepared with labeled gramicidin, the oriented samples result in high-resolution 15N NMR spectra showing 12 resonances for the 20 nitrogen sites of the polypeptide. The frequency of the three major multiple resonance peaks has been interpreted to yield the approximate orientation of the N-H bonds in the peptide linkages with respect to the magnetic field. These bond orientations are only partially consistent with the extant structural models of gramicidin. 相似文献
3.
Reversible succinate dehydrogenase (SDH) activities have been ubiquitously detected in organisms from the three domains of life. They represent constituents either of respiratory complexes II in aerobes, or of fumarate dehydrogenase complexes in anaerobes. The present review gives a survey on archaeal succinate:quinone oxidoreductases (SQRs) analyzed so far. Though some of these could be studied in detail enzymologically and spectroscopically, the existence of others has been deduced only from published genome sequences. Interestingly, two groups of enzyme complexes can be distinguished in Archaea. One group resembles the properties of SDHs known from bacteria and mitochondria. The other represents a novel class with an unusual iron-sulfur cluster in subunit B and atypical sequence motifs in subunit C which may influence electron transport mechanisms and pathways. This novel class of SQRs is discussed in comparison to the so-called 'classical' complexes. A phylogenetic analysis is presented suggesting a co-evolution of the flavoprotein-binding subunit A and subunit B containing the three iron-sulfur clusters. 相似文献
4.
Nikolas K. Haass D. Ripperger E. Wladykowski P. Dawson P. A. Gimotty C. Blome F. Fischer P. Schmage I. Moll Johanna M. Brandner 《Histochemistry and cell biology》2010,133(1):113-124
Melanoma depends on, interacts with and reacts to the stroma in which it is embedded, including fibroblasts, extracellular
matrix, endothelial cells and immune cells. However, the impact of melanoma on the epidermal tumor microenvironment—the multilayered
epithelium of the skin—is poorly understood. Gap junctions are essential for intercellular communication and involved in proliferation,
differentiation and homeostasis of keratinocytes. We have shown previously that the gap junction proteins connexin 26 and
30 (Cx26 and Cx30) are induced in the epidermal tumor microenvironment of skin cancers including melanoma. This study compares
the extent of Cx26, Cx30 and Cx43 expression in the epidermal microenvironment of melanocytic nevi and melanomas and its association
with melanoma thickness, proliferative index of the tumor and its microenvironment, and with 5-year metastasis and survival.
We found that induction of Cx26 and Cx30 cell–cell border expression in the epidermal tumor microenvironment correlates to
malignancy. Importantly, there was a significant correlation of tumor thickness with the vertical epidermal Cx26 and Cx30
expression pattern and the horizontal Cx26 dissemination. Furthermore, horizontal Cx26 expression correlated with metastasis.
Vertical epidermal expression patterns of Cx26 and Cx30 significantly correlated with the proliferative index in the epidermal
tumor microenvironment but not with the proliferative index in the tumor. In contrast, Cx43 did not correlate with malignancy,
thickness or proliferative index. In summary, here we show for the first time a significant association between the progression
of melanoma and alterations in its epithelial tumor microenvironment. 相似文献
5.
Phosphorylation of Thylakoid Proteins of Oryza sativa: In Vitro Characterization and Effects of Chilling Temperatures
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The phosphorylation of thylakoid proteins of rice (Oryza sativa L.) was studied in vitro using [γ-32P]ATP. Several thylakoid proteins are labeled, including the light-harvesting complex of photosystem II. Protein phosphorylation is sensitive to temperature, pH, and ADP, ATP, and divalent cation concentrations. In the range pH 7 to 8.2, phosphorylation of the light-harvesting polypeptides declines above pH 7.5, whereas labeling of several other thylakoid polypeptides increases. Increasing divalent cation concentration from 3 to 20 millimolar results in a decrease in phosphorylation of the 26 kilodalton light-harvesting complex polypeptide and increased phosphorylation of several other polypeptides. ADP has an inhibitory effect on the phosphorylation of the light-harvesting complex polypeptides. Phosphorylation of the 26 kilodalton light-harvesting polypeptide requires 0.45 millimolar ATP for half-maximal phosphorylation, compared to 0.3 millimolar for the 32 kilodalton phosphoprotein. Low temperature inhibits the phosphorylation of thylakoid proteins in chilling-sensitive rice. However, phosphorylation of histones by thylakoid-bound kinase(s) is independent of temperature in the range of 25 to 5°C, suggesting that the effect of low temperature is on accessibility of the substrate, rather than on the activity of the kinase. 相似文献
6.
Hans W. Heid Ingrid Moll Werner W. Franke 《Differentiation; research in biological diversity》1988,37(3):215-230
The hair-forming cells (trichocytes) and the mature hair contain four major trichocytic cytokeratins from each of the subfamilies, basic (Hb1-4) and acidic (Ha1-4); these are related - but not identical - to the epithelial cytokeratins. Here we show, by biochemical methods and immunofluorescence microscopy using antibodies specific for either epithelial or trichocyte cytokeratins, that the same set of hair-type cytokeratins, including two newly identified minor components, designated Hax (type I) and Hbx (type II), are also expressed in cells forming nails, in the filiform papillae of the dorsal surface of human and bovine tongue, and, most surprisingly, in some cells of the epithelial reticulum of bovine and human thymus. By double-label immunofluorescence microscopy, we also show that the expression of the two subsets of cytokeratins, i.e., the epithelial and the trichocytic ones, is not necessarily mutually exclusive, but that certain cells of hair follicles, nail matrix and bed, lingual papillae, and the nonlymphoid cell system of the thymus contain both trichocytic and certain epithelial cytokeratins. This indicates that these cells coexpress representatives of both kinds of cytokeratin. Implications of these findings with respect to problems of regulatory control of cytokeratin synthesis in tissue development and differentiation, and the possible functional meaning of the occurrence of trichocytic cytokeratins in such histologically diverse tissues, are discussed. 相似文献
7.
Tarun Ghose Soldano Ferrone A. Huntley Blair Yaroslav Kralovec Massimo Temponi Mandip Singh Moll Mammen 《Cancer immunology, immunotherapy : CII》1991,34(2):90-96
Summary Intravenous injections into nude mice of 5 mg/kg methotrexate (MTX) linked to the antibody to human high molecular weight-melanoma associated antigen (HMW-MAA), monoclonal antibody (mAb) 225.28, an IgG2a, on days 1, 4, 7, 10 and 14, starting 24 h after subcutaneous inoculation of 2 × 106 cultured human M21 melanoma cells inhibited mean tumor volume by 90% on day 14 and by 65% on day 50 after the beginning of the treatment. Injections of equimolar amounts of free MTX and MTX linked to normal mouse IgG or to an isotypematched myeloma protein did not inhibit tumor growth significantly. MTX linked to mAb 225.28 did not inhibit the xenograft of a subline of human melanoma cell line M21 without detectable expression of HMW-MAA. In a clonogenic assay, the MTX-225.28 conjugate was three times more potent in inhibiting the growth of M21 melanoma cells than free MTX, but did not inhibit the growth of kidney carcinoma cells Caki-1, which do not express high-M
r MAA. In contrast, MTX linked to the mAb DAL K29, reacting with kidney carcinoma cells Caki-1, inhibited their growth but did not affect that of melanoma cells. M21 melanoma cells isolated from the residual tumor of a mouse treated with the MTX-225.28 conjugate did not differ in their reactivity with mAb 225.28 and in their sensitivity to MTX when compared with M21 cells from an untreated mouse. 相似文献
8.
M D Kramer L Binninger V Schirrmacher H Moll M Prester G Nerz M M Simon 《Journal of immunology (Baltimore, Md. : 1950)》1986,136(12):4644-4651
We describe the characterization and purification of a trypsin-like serine protease isolated from cloned long-term culture cytolytic T cell line (CTLL AK). High amounts of proteolytic activity were isolated from extracts of CTLL AK after either nitrogen cavitation or detergent lysis. Trypsin-like protease was detected by using either the ester compound N alpha-benzyloxycarbonyl-L-lysine thiobenzyl ester or a panel of low molecular amide substrates. The latter compounds were preferentially cleaved at the carboxyl termini of lysine and arginine residues. The enzyme activity was completely inhibited by two serine esterase inhibitors, diisopropylfluorophosphate and phenylmethanesulfonyl fluoride, and by aprotinin and meta-aminobenzamidine, which are known to block trypsin-like proteases. The pH optimum for CTLL AK-derived protease activity is 8 to 9. Analysis of the enzyme by gel filtration revealed that the cell-bound proteolytic activity was associated with a complex that could not be dissociated by treatment with Triton X-100. The CTLL AK-derived protease activity was found to reside in two proteins with relative molecular masses (Mr) of 32,000 and 40,000 daltons as determined by affinity labeling with [3H]diisopropylfluorophosphate and sodium dodecyl sulfate gel electrophoresis. High levels of enzyme activity were found in a panel of H-Y-specific cloned T cell lines with either cytolytic/suppressor (CTLL) or helper potential (THL), indicating a lack of correlation between trypsin-like protease activity and a particular T cell function. High enzyme activity was also detected in tumorigenic variants of CTLL. Furthermore, it was excluded that the trypsin-like activity detected was attributable to plasminogen activator activity. In contrast to cloned T effector cells and their in vitro or in vivo derived variants, considerably less activity was found in normal nonactivated or activated lymphocyte populations. The possible role of the trypsin-like serine protease in the function of T effector cells is discussed. 相似文献
9.
JoséL. Jorcano Michael Rieger Juergen K. Franz Dorothea L. Schiller Roland Moll Werner W. Franke 《Journal of molecular biology》1984,179(2):257-281
Cytoskeletal filaments of the α-keratin type (cytokeratins) are a characteristic of epithelial cells. In diverse mammals (man, cow and rodents) these cytokeratins consist of a family of approximately 20 polypeptides, which may be divided into the more acidic (I) and the more basic (II) subfamilies. These two subfamilies show only limited amino acid sequence homology. In contrast, nucleic acid hybridization experiments and peptide maps have been interpreted to show that polypeptides of the same subfamily share extended sequence homology.We compare two polypeptides of the acidic cytokeratin subfamily, VIb (Mr 54,000) and VII (Mr 50,000), which are co-expressed in large amounts in bovine epidermal keratinocytes. These two epidermal keratins can be distinguished by specific antibodies and show different patterns of expression among several bovine tissues and cultured cells. In addition, they differ in the stability of their complexes with basic keratin polypeptides and in their tryptic peptide maps. The amino acid sequences deduced from the nucleotide sequences of complementary DNA clones containing the 3′ ends of the messenger RNAs for these keratins are compared with each other and with available amino acid sequences of human, murine and amphibian epidermal keratins. Bovine keratins VIb and VII share considerable sequence homology in the α-helical portion (68% residues identical) but lack significant homology in the extrahelical portion. Bovine keratin VIb shows, in its α-helical region, a pronounced sequence homology (88% identity) to the murine epidermal keratin of Mr 59,000. In addition, the non-helical carboxy-terminal regions of both proteins are glycinerich and contain a canonic sequence GGGSGYGG, which may be repeated several times. Moreover, their mRNAs present a highly conserved stretch of 236 nucleotides containing, in the murine sequence, the end of the coding and all of the non-coding region (81% identical nucleotides). Bovine keratin VII is considerably different from the murine Mr 59,000 keratin but is almost identical to the human cytokeratin number 14 of Mr 50,000, both in the α-helical and in the non-α-helical regions of the proteins, and the mRNAs of the human and the bovine keratins also display a high homology in their 3′ non-coding ends.The results show that in the same species keratins of the same subfamily can differ considerably, whereas equivalent keratin polypeptides of different species are readily identified by characteristic sequence homologies in the α-helical and the non-helical regions as well as in the 3′ non-coding portions of their mRNAs. Among the members of the acidic subfamily I of cytokeratin polypeptides that are co-expressed in bovine epidermis, at least two types can be distinguished by their carboxy-terminal sequences. One type is characterized by its abundance of glycine residues, a consensus GGGSGYGG heptapeptide sequence, which may be repeated several times, and an extended stretch of high RNA sequence homology in the 3′ non-coding part. The other type shows a predominance of serine and valine residues, a subterminal GGGSGYGG sequence (which has been maintained in Xenopus, cow and man) and also a high level of homology in the 3′ non-coding part of the mRNA. The data indicate that individual keratin type specificity overrides species diversity, both at the protein and the mRNA level. We discuss the evolutionary conservation and the tissue distribution of these two types of acidic keratin polypeptides as well as their possible biological functions. 相似文献
10.
Kinetics of malt starch hydrolysis by endogeneous alpha- and beta-amylases has been experimentally investigated in laboratory-, pilot- and industrial-scale reactors. The production rates of glucose, maltose, maltotriose and total extract, and the separate alpha- and beta-amylases deactivation rates are measured at varying mashing temperature and different initial starch concentrations and qualities. Based on the experimental results, a model is proposed that takes into account the initial carbohydrates and enzymes dissolution, the starch gelatinization, the separate hydrolytic action of alpha-and beta-amylases on insoluble and soluble starch and dextrins, and the influence of temperature both on enzyme activities and thermal denaturation rate. The model can predict, at the three scales, the final sugars concentrations in the wort for given initial malt concentrations and enzymatic contents, and for a fixed temperature profile during the mashing process. 相似文献