排序方式: 共有56条查询结果,搜索用时 15 毫秒
1.
During the past decade proteases have been widely used as catalysts in peptide synthesis. Unfortunately, they are not ideal ligases. Enzymatic peptide synthesis in frozen aqueous systems has been developed as an approach towards the suppression of competitive reactions. This paper summarizes reports concerning the behaviour of non-enzymatic as well as of enzyme-catalysed reactions when the reaction mixture is frozen. The advantages of freezing the reaction mixture in serine and cysteine protease-catalysed peptide synthesis, the influence of modified reaction conditions and the possible reasons for the yield-increasing effect of freezing are discussed. 相似文献
2.
The Drosophila melanogaster gene flightless-I, involved in gastrulation and
muscle degeneration, has Caenorhabditis elegans and human homologues. In
these highly conserved genes, two previously known gene families have been
brought together, families encoding the actin- binding proteins related to
gelsolin and the leucine-rich-repeat (LRR) group of proteins involved in
protein-protein interactions. Both these gene families exhibit
characteristics of molecular changes involving replication slippage and
exon shuffling. Phylogenetic analyses of 19 amino acid sequences of 6
related protein types indicate that actin- associated proteins related to
gelsolin are monophyletic to a common ancestor and include flightless
proteins. Conversely, comparison of 24 amino acid sequences of LRR proteins
including the flightless proteins indicates that flightless proteins are
members of a structurally related subgroup. Included in the flightless
cluster are human and mouse rsp-1 proteins involved in suppressing v-Ras
transformation of cells and the membrane-associated yeast (Saccharomyces
cerevisae) adenylate cyclase whose analogous LRRs are required for
interaction with Ras proteins. There is a strong possibility that ligands
for this group could be related and that flightless may have a similar role
in Ras signal transduction. It is hypothesized that an ancestral monomeric
gelsolin precursor protein has undergone at least four independent gene
reorganization events to account for the structural diversity of the extant
family of gelsolin-related proteins and that gene duplication and exon
shuffling events occurred prior to or at the beginning of multicellular
life, resulting in the evolution of some members of the family soon after
the appearance of actin-type proteins.
相似文献
3.
N. Sewald W. Hollweck K. Mütze C. Schierlinger L. C. Seymour K. Gaa K. Burger B. Koksch H. D. Jakubke 《Amino acids》1995,8(2):187-194
Summary Methodology for the synthesis and incorporation of-trifluoromethyl substituted amino acids into N- and C-terminal position of peptides is described. The incorporation of-trifluoromethyl substituted amino acids into strategical positions of peptides enhances proteolytic stability and lipophilicity. Furthermore, it improves transport rates in vivo and permeability through certain body barriers. 相似文献
4.
Magnesium-induced inner membrane aggregation in heart mitochondria: prevention and reversal by carboxyatractyloside and bongkrekic acid
下载免费PDF全文
![点击此处可从《The Journal of cell biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Mg(2+) at an optimal concentration of 2mM (ph 6.5) induces large increases (up to 30 percent) in the optical density of bovine heart mitochondria incubated under conditions of low ionic strength (< approx. 0.01). The increases are associated with aggregation (sticking together) of the inner membranes and are little affected by changes in the energy status of the mitochondria. Virtually all of a number of other polyvalent cations tested and Ag(+) induce increases in mitochondrial optical density similar to those induced by Mg(2+), their approximate order of concentration effectiveness in respect to Mg(2+) being: La(3+) > Pb(2+) = Cu(2+) > Cd(2+) > Zn(2+) > Ag(+) > Mn(2+) > Ca(2+) > Mg(2+). With the exception of Mg(2+), all of these cations appear to induce swelling of the mitochondria concomitant with inner membrane aggregation. The inhibitors of the adenine nucleotide transport reaction carboxyatratyloside and bongkrekic acid are capable of preventing and reversing Mg(2+)-induced aggregation at the same low concentration required for complete inhibition of phosphorylating respiration, suggesting that they inhibit the aggregation by binding to the adenine nucleotide carrier. The findings are interpreted to indicate (a) that the inner mitochondrial membrane is normally prevented from aggregating by virtue of its net negative outer surface change, (b) that the cations induce the membrane to aggregate by binding at its outer surface, decreasing the net negative charge, and (c) that carboxyatractyloside and bongkrekic acid inhibit the aggregation by binding to the outer surface of the membrane, increasing the net negative charge. 相似文献
5.
Gololobov MY Kozlova EV Borisov IL Schellenberger U Schellenberger V Jakubke HD 《Biotechnology and bioengineering》1992,40(3):432-436
The published theory of kinetically controlled enzymatic peptide synthesis needed experimental verification. We carried out the measurement of the peptide yield and estimation of the key parameters alpha and beta for papain-catalyzed synthesis of Mal-L-Phe-L-Ala-LLeuNH(2) from Mal-L-Phe-L-AlaOMe and L-LeuNH(2). The experimental results demonstrate that this theory adequately describes the real process. (c) 1992 John Wiley & Sons, Inc. 相似文献
6.
We investigated the alpha-chymotrypsin-catalyzed acyl transfer to a series of glycine oligomers. It could be established that the electrostatic interactions between the carboxylate group of the nucleophiles and the S'-subsites of the enzyme fall off with the length of the nucleophile molecule. Additional negatively charged residues in the nucleophile lead to a considerable reduction of the acyl transfer efficiency. An arginine residue in P'1- or P'3-position, but not in P'2-position, makes favourable interactions with the appropriate S'-subsites of the enzyme. 相似文献
7.
Characterization of the S'-subsite specificity of V8 proteinase via acyl transfer to added nucleophiles 总被引:1,自引:0,他引:1
M Schuster A Aaviksaar V Schellenberger H D Jakubke 《Biochimica et biophysica acta》1990,1036(3):245-247
The S'-subsite specificity of endoproteinase Glu-C (V8 proteinase) was studied by acyl transfer reactions using Z-Glu-OMe as acyl donor and a series of amino acid- and peptide-derived nucleophiles. The partition constant, which characterizes specificity, was determined by a method based on the integrated rate equation. V8 proteinase prefers amino acid residues with hydrophobic side chains in the P'1 position. Di- and tripeptide amides are more efficient nucleophilic amino components than amino acid amides. 相似文献
8.
Marion Haensler Heike Schuerer Ulrich Hahn Hans-Dieter Jakubke 《Nucleosides, nucleotides & nucleic acids》2013,32(7):1267-1274
Abstract Synthesis of guanylyl(3′→5′)cytidine catalysed by RNase T1 variants (Tyr42Trp, Tyr24Trp and GluSSAla) was studied in frozen aqueous systems at-10°C and in solution at 0°C. Freezing the reaction mixture resulted in significantly enhanced dinucleoside monophosphate yields independently of the effect of mutation on substrate binding and catalytic mechanism. We assume that the protonation state of the catalytic residues is influenced by freezing, possibly due to conformational changes of the enzyme proteins. 相似文献
9.
Rates and patterns of evolution in partial sequences of five mitochondrial
genes (cytochrome b, ATPase 6, NADH dehydrogenase subunit 5, tRNA(Glu), and
the control region) were compared among taxa in the passerine bird genera
Fringilla and Carduelis. Rates of divergence do not vary significantly
among genes, even in comparisons with the control region. Rate variation
among lineages is significant only for the control region and NADH
dehydrogenase subunit 5, and patterns of variation are consistent with the
expectations of neutral theory. Base composition is biased in all genes but
is stationary among lineages, and there is evidence for directional
mutation pressure only in the control region. Despite these similarities,
patterns of substitution differ among genes, consistent with alternative
regimes of selective constraint. Rates of nonsynonymous substitution are
higher in NADH dehydrogenase subunit 5 than in other protein-coding genes,
and transitions exist in elevated proportions relative to transversions.
Transitions appear to accumulate linearly with time in tRNA(Glu), and
despite exhibiting the highest overall rate of divergence among species,
there are no transversional changes in this gene. Finally, for resolving
phylogenetic relationships among Fringilla taxa, the combined
protein-coding data are broadly similar to those of the control region in
terms of phylogenetic informativeness and statistical support.
相似文献
10.