Home  About us  Contact
 

Heterodimeric Form (heterodimeric + form)

Distribution by Scientific Domains
Life Sciences50%
Chemistry50%

Selected Abstracts

Bifunctional indole-3-acetyl transferase catalyses synthesis and hydrolysis of indole-3-acetyl- myo -inositol in immature endosperm of Zea mays

PHYSIOLOGIA PLANTARUM, Issue 2 2003
Stanislaw Kowalczyk
1- O -(indole-3-acetyl)- , - d -glucose: myo -inositol indoleacetyl transferase (IA- myo -inositol synthase) is an important enzyme in IAA metabolism. This enzyme catalyses the transfer of the indole acetyl (IA) moiety from 1- O -(indole-3-acetyl)- , - d -glucose to myo -inositol to form IA- myo- inositol and glucose. IA- myo -inositol synthase was purified to an electrophoretically homogenous state from maize liquid endosperm by fractionation with ammonium sulphate, anion-exchange, adsorption on hydroxylapatite, affinity chromatography on ConA-Sepharose, preparative PAGE and isoelectric focusing. We thus obtained two enzyme preparations which differ in their Rf on 8% polyacrylamide gel. The preparation of Rf 0.36 contained a single 56.4 kDa polypeptide, whereas the preparation of Rf 0.39 consisted of two polypeptides of 56.4 and 53.5 kDa. Both purified preparations of IAInos synthase also exhibited the activity of an IAInos hydrolase, showing that the dual activity was associated with a single protein. Results of gel filtration and analytical SDS-PAGE suggest that the native enzyme exists as both a monomeric (65 kDa) and homo- or heterodimeric form (110,130 kDa). Analysis of peptide maps and amino acid sequences of two 21 amino-acid peptides showed that polypeptides of 56.4 and 53.5 kDa have the same primary structure and that the 3 kDa difference in molecular mass is probably caused by different glycosylation levels. Comparison of this partial and internal amino acid sequence with sequences of other plant acyltransferases indicated similarity to several proteins which belonged to the serine carboxypeptidase-like (SCPL) acyltransferase family. [source]

The production, purification and crystallization of a soluble heterodimeric form of a highly selected T-­cell receptor in its unliganded and liganded state

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 12 2002
Craig S. Clements
T-cell antigen receptors (TcRs) are heterodimeric cell-surface receptors that play a pivotal role in the cellular immune response. The TcR interacts specifically with a peptide-laden major histocompatability complex (pMHC). A human TcR has been characterized that interacts with an immunodominant epitope, FLRGRAYGL, from the Epstein,Barr virus, a ubiquitous human pathogen, in complex with HLA-B8. Despite the vast TcR repertoire, this TcR is found in up to 10% of the total T-cell population in seropositive HLA-B8+ individuals. In this report, this highly selected TcR is characterized by expressing in Escherichia coli, refolding, purifying and crystallizing the receptor. In addition, the HLA-B8,FLRGRAYGL complex has been expressed in E. coli, refolded and shown to be functionally active. Using native gel electrophoresis, the refolded TcR is shown to be capable of binding specifically to the refolded HLA-B8,FLRGRAYGL and this TcR has been crystallized in complex with the pMHC. The crystals of the unliganded and liganded TcR diffract to 1.5 and 2.5,Å, respectively. [source]

Production of Functional Hepatocyte Growth Factor (HGF) in Insect Cells Infected with an HGF-Recombinant Baculovirus in a Serum-Free Medium

BIOTECHNOLOGY PROGRESS, Issue 2 2000
Min-Ying Wang
Three insect cell lines, SL-7B cells derived from Spodoptera litura, Sf9, and High Five (Hi-5) cells, were used for the production of pro-hepatocyte growth factor (pro-HGF). Cells were cultured and then infected with a recombinant HGF-containing baculovirus in a serum-free medium. In SL-7B cells, pro-HGF is synthesized and excreted from the cells and late in infection is converted to a heterodimeric form of HGF even when the cells are grown in serum free medium. Conversion of a single-chain form of HGF (pro-HGF) into an HGF heterodimer was unexpected, as pro-HGF is normally cleaved by a serum protease called HGF activator. The proliferation activity of heparin-affinity-purified HGF from serum-free culture supernatant of SL-7B cells is comparable to that obtained from HGF converted by serum proteases, suggesting that SL-7B cells produce a functionally analogous protease to correctly process pro-HGF. This work reports, for the first time, on the feasibility of properly processing pro-HGF to form functional HGF by proteases from invertebrate cells in serum-free media. Avoiding the supplementation of sera provides the advantages of a low production cost, zero contamination of infectious agents from sera, and simple downstream product purification. Experimental results further demonstrate that the conversion of pro-HGF by insect cells is cell-line-dependent, because proteases in Hi-5 or Sf9 cells could not process pro-HGF as efficiently and properly as those in SL-7B cells. [source]

Critical role of C/EBP, and C/EBP, factors in the stimulation of the cyclooxygenase-2 gene transcription by interleukin-1, in articular chondrocytes

FEBS JOURNAL, Issue 23 2000
Béatrice Thomas
The activity of the [,831; +103] promoter of the human cyclooxygenase-2 gene in cultured rabbit chondrocytes is stimulated 2.9 ± 0.3-fold by interleukin-1, and this stimulation depends on [,132; ,124] C/EBP binding-and [,223; ,214] NF-,B binding-sites. The C/EBP, and C/EBP, factors bind to the [,132; ,124] sequence. The [,61; ,53] sequence is also recognized by C/EBP, and C/EBP, as well as USF. Mutation of the whole [,61; ,53] sequence abolished the stimulation of transcription but single mutations of the C/EBP or USF site did not alter the activity of the promoter, suggesting that the factors bound to the proximal [,61; ,53] sequence interact with different members of the general transcription machinery. The [,223; ,214] site binds only the p50/p50 homodimer and a non-rel-related protein, but not the transcriptionally active heterodimer p50/p65. The p50/p50 homodimer could interact with the C/EBP family members bound to the [,132; ,124] sequence for full stimulation of the COX-2 transcription by interleukin-1, in chondrocytes. By contrast, the [,448; ,449] sequence binds with a low affinity both the p50/p50 homodimeric and p50/p65 heterodimeric forms of NF-,B but has no role in the regulation of the human COX-2 promoter in chondrocytes. [source]