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1.
J Bello E N Granados S Lewinski H R Bello T Trueheart 《Journal of biomolecular structure & dynamics》1985,2(5):899-913
Methylated lysine, arginine and histidine residues are found in a number of proteins (for example, histones, non-histone chromosomal proteins, ribosomal proteins, calmodulin, cytochrome C, etc.). We are studying the effects of methylation on the conformations of poly(lysine) and of the effects of methylation of poly(lysine) and poly(arginine) on interactions with polynucleotides. The conformational properties of epsilon-amino-methylated poly(lysine) differ from those of unmodified poly(lysine). Methylation increases resistance to thermally-induced and NaCl-induced changes in the CD spectrum. Guanidinium chloride increases (proportional to the degree of methylation) the extent of approach to the conformation in dispute as to its being a random coil or an extended helix. Methylation enhances aggregation in the helix-inducing solvent 0.5 M Ca(ClO4)2. With increasing methylation of poly(lysine), the conformation in dodecyl sulfate changes from beta, to 50% alpha, to random coil at the maximum methylation. Increasing methylation of poly(lysine) weakens the interaction with polynucleotides in respect to dissociation by salt, linearly with methyl content. Complexes of (dAdT)n.(dAdT)n with the polypeptides are increasingly stabilized to heat denaturation by progressive methylation. However, with a series of synthetic double-stranded RNA's and DNA's a more complex situation exists, Tm increasing or decreasing, depending on the base composition, sequence and type of sugar. Methylation of poly(lysine) and poly(arginine) can have opposite effects on Tm based on results with complexes with (dI)n.(dC)n. Methylated poly(lysine) affects the CD spectrum of polynucleotides, in a manner dependent on base composition and sequence. In some cases large positive or negative psi-spectra are induced, which, in the case of (dGdC)n.(dGdC)n, can be positive or negative depending on the degree of methylation of the polypeptide and the salt concentration. It is suggested that the biological effects of methylation proteins may be evoke by salt changes in the cell cycle, and that methylation can affect local interactions with nucleic acids and larger scale structure, and interactions with lipids. 相似文献
2.
Structure-activity relationship of swainsonine. Inhibition of human alpha-mannosidases by swainsonine analogues. 总被引:1,自引:1,他引:0
I Cenci di Bello G Fleet S K Namgoong K Tadano B Winchester 《The Biochemical journal》1989,259(3):855-861
The inhibitory properties of a series of synthetic epimers and analogues of swainsonine towards the multiple forms of human alpha-mannosidases were studied in vitro and in cells in culture. Of the five epimers tested, only the 8a-epimer and 8,8a-diepimer of swainsonine were specific and competitive inhibitors (Ki values of 7.5 x 10(-5) and 2 x 10(-6) M respectively) of lysosomal alpha-mannosidases in vitro and induced storage of mannose-rich oligosaccharides in human fibroblasts in culture. The structures of these storage products indicated that processing alpha-mannosidases had also been inhibited. This was consistent with the observed inhibition in vitro of these enzymes by these compounds. In contrast, the 8-epimer, 1,8-diepimer and 2,8a-diepimer of swainsonine had no appreciable effect on any alpha-mannosidases. The corresponding open-chain analogues of swainsonine, namely 1,4-dideoxy-1,4-imino-D-mannitol, of the 8a-epimer, namely 1,4-dideoxy-1,4-imino-D-talitol, and of the 8,8a-diepimer, namely 1,4-dideoxy-1,4-imino-L-allitol, were weaker competitive inhibitors of lysosomal alpha-mannosidase, with Ki values of 1.3 x 10(-5), 1.2 x 10(-4) and 1.2 x 10(-4) M respectively. These analogues also proved less effective at inducing oligosaccharide accumulation and in disturbing glycoprotein processing. These compounds offer the opportunity to determine which alterations in the chirality of the swainsonine molecule affect its inhibitory specificity. A comparison of their biological activities has identified reagents that will be useful for studying steps in the biosynthesis and catabolism of glycoproteins and that may be of potential value in chemotherapy. 相似文献
3.
4.
Replication of repeated DNA in human cells 总被引:1,自引:0,他引:1
The replication pattern of the repeated sequence families of human DNA has been studied by means of DNA reassociation curves. Early- and late-replicating DNA fractions were obtained from synchronized cultures of KB cells by labeling cells with bromodeoxyuridine (BUdR) early or late in the DNA synthesis period and isolating the BUdR-containing DNA by CsCl density-gradient centrifugation. Highly repeated and moderately repeated sequence classes labeled with either early or late in the DNA synthesis period were also prepared. The effect of the isolated early- or late-replicating BUdR-DNA on the rate of reassociation of the repeated sequences was then tested. Increasing concentrations of early- or late-replicating BUdR-DNA were added to a constant amount of either early- or late-replicating repeated sequences, and the fraction of label in double-stranded DNA was determined. Analysis of the DNA reassociation curves so obtained indicates that some repeated sequence families are replicated throughout the DNA synthesis period whereas others are replicated primarily in the second half. This is true for both the highly-repeated and moderately-repeated sequence classes. 相似文献
5.
Summary A comparative study of the association of mitotic acrocentric chromosomes and acrocentric bivalents at the pachytene stage shows that at least two factors can act in the associative behaviour of these chromosomes: (1) Nor activity and (2) the presence of satellite DNA in the short arms of these chromosomes. These factors do not act with the same intensity in the two cell lines studied. In lymphocytes, Nor activity prevails, whereas satellite DNA plays the main role in the association of acrocentric chromosomes in germ cells at the pachytene stage. 相似文献
6.
Importance of neurophysin dimer and of tyrosine-49 in the binding of neurohypophyseal peptides 总被引:1,自引:0,他引:1
P Nicolas J Wolff M Camier C Di Bello P Cohen 《The Journal of biological chemistry》1978,253(8):2633-2639
7.
Mouse lymphoid cells and tumor cell lines were employed as target cells for the investigation of the mechanism of heterocytotoxicity in human serum samples. It was shown that the heterocytotoxic effects were due to two differing mechanisms. Cytotoxicity was mediated in part, by activation of the alternative complement pathway on target cell membrane, a process which was antibody-independent. A second mechanism of cytotoxicity was induced by natural antibodies to a target cell, which probably mediated activation of the classical complement pathway. These data may shed light on the frequently observed cytotoxicity in mammalian sera for various target cells. 相似文献
8.
G Del Boccio A Pennelli E P Whitehead M Lo Bello R Petruzzelli G Federici G Ricci 《The Journal of biological chemistry》1991,266(21):13777-13782
7-Chloro-4-nitrobenzo-2-oxa-1,3-diazole reacts with two thiol groups of the dimeric horse erythrocyte glutathione transferase at pH 5.0, with strong inactivation reversible on dithiothreitol treatment. The inactivation kinetic follows a biphasic pattern, similar to that caused by other thiol reagents as recently reported. Both S-methylglutathione and 1-chloro-2,4-dinitrobenzene protect the enzyme from inactivation. Analysis of the reactive SH group-containing peptide gives the sequence Ala-Ser-Cys-Leu-Tyr, identical with that of the peptide that contains the reactive cysteine 47 of the human placental transferase. In the presence of glutathione, the enzyme is not inactivated by this reagent, but it catalyzes its conjugation to glutathione. At higher pH values, 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole reacts with 2 tyrosines/dimer and lysines, as well as with cysteines. Reaction with lysine seems essentially without effect on activity; whether the reactive tyrosines are important for activity could not be determined using this reagent only. However, 2 tyrosines among the 4 that are nitrated by tetranitro-methane are important for activity. 相似文献
9.
C Di Bello A Scatturin G D'Auria M Gargiulo L Paolillo E Trivellone R De Castiglione 《Biopolymers》1991,31(6):643-652
The conformational properties of spantide [(D-Arg, D-Trp, Leu) substance P] have been studied by fluorescence, CD, and nmr techniques. The fluorescence, CD, and nmr parameters in different solvents and in a micellar environment (SDS) are compared with the data collected for bombesin. A preliminary investigation on [D-Pro] spantide is also reported. 相似文献
10.