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ATP-binding Domain (ATP-bind + domain)
Selected AbstractsTyrosine kinase inhibitors: From rational design to clinical trialsMEDICINAL RESEARCH REVIEWS, Issue 6 2001Peter Traxler Abstract Protein kinases play a crucial role in signal transduction as well as in cellular proliferation, differentiation, and various regulatory mechanisms. The inhibition of growth related kinases, especially tyrosine kinases, might provide new therapies for diseases such as cancer. The progress made in the crystallization of protein kinases has confirmed that the ATP-binding domain of tyrosine kinases is an attractive target for drug design. Three successful examples of drug design at Novartis using a tyrosine kinase as a molecular target are described. PKI166, a pyrrolo[2,3,- d]pyrimidine derivative, is a dual inhibitor of both the EGFR and the ErbB2 kinases. The compound entered clinical trials in 1999, based on its favorable preclinical profile: potent inhibition of EGF-mediated signalling in cells, in vivo antitumor activity in several EGFR overexpressing xenograft tumor models in nude mice, long-lasting inhibition of EGF-stimulated EGFR autophosphorylation in tumor tissue, good oral bioavailability in animals, and no prohibitive in vitro and in vivo toxicity findings. The anilino-phthalazine derivative PTK787/ZK222584 (Phase I, co-developed by Schering AG, Berlin) is a potent and selective inhibitor of both the KDR and Flt-1 kinases with interesting anti-angiogenic and pharmacokinetic properties (orally bioavailable). STI571 (GlivecÔ, GleevecÔ), a phenylamino-pyrimidine derivative, is a potent inhibitor of the Abl tyrosine kinase, which is present in 95% of patients with chronic myelogenous leukemia (CML). The compound specifically inhibits proliferation of v-Abl and Bcr-Abl expressing cells (including cells from CML patients) and shows anti-tumor activity as a single agent in animal models at well-tolerated doses. Pharmacologically relevant concentrations are achieved in the plasma of animals (oral administration). Promising data from phase I and II clinical trials in CML patients (98% haematological response rate in Phase I) support the fact that the STI571 represents a new treatment modality for CML. In addition, potent inhibition of the PDGFR and c-Kit tyrosine kinases also indicates its possible clinical use in solid tumors. © 2001 John Wiley & Sons, Inc. Med Res Rev, 21, No. 6, 499,512, 2001 [source] A six amino acid deletion, partially overlapping the VanSB G2 ATP-binding motif, leads to constitutive glycopeptide resistance in VanB-type Enterococcus faeciumMOLECULAR MICROBIOLOGY, Issue 3 2003Florence Depardieu Summary Enterococcus faecium clinical isolate BM4524, resistant to vancomycin and susceptible to teicoplanin, harboured a chromosomal vanB cluster, including the vanSB / vanRB two-component system regulatory genes. Enterococcus faecium strain BM4525, isolated two weeks later from the same patient, was resistant to high levels of both glycopeptides. The ddl gene of BM4525 had a 2 bp insertion leading to an impaired d -alanine: d -alanine ligase. Sequencing of the vanB operon in BM4525 also revealed an 18 bp deletion in the vanSB gene designated vanSB, . The resulting six amino acid deletion partially overlapped the G2 ATP-binding domain of the VanS B, histidine kinase leading to constitutive expression of the resistance genes. Sequence analysis indicated that the deletion occurred between two tandemly arranged heptanucleotide direct repeats, separated by 11 base-pairs. The VanS B , VanS B, and VanR B proteins were overproduced in Escherichia coli and purified. In vitro autophosphorylation of the VanS B and VanS B, histidine kinases and phosphotransfer to the VanR B response regulator did not differ significantly. However, VanS B, was deficient in VanR B phosphatase activity leading to accumulation of phosphorylated VanR B . Increased glycopeptide resistance in E. faecium BM4525 was therefore a result of the lack of production of d -alanyl- d -alanine ending pentapeptide and to constitutive synthesis of d -alanyl- d -lactate terminating peptidoglycan precursors, following loss of d -alanine: d -alanine ligase and of VanS B phosphatase activity respectively. We suggest that the heptanucleotide direct repeat in vanSB may favour the appearance of high level constitutively expressed vancomycin resistance through a ,slippage' type of genetic rearrangement in VanB-type strains. [source] Crystallization and preliminary X-ray characterization of a catalytic and ATP-binding domain of a putative PhoR histidine kinase from the ,-radioresistant bacterium Deinococcus radioduransACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 4 2010S. Caria The gene product of histidine kinase DR2244 (putative phoR) encoded by Deinococcus radiodurans has been suggested to be involved in the PhoR,PhoB two-component regulatory system. This two-component signalling system is activated upon phosphate starvation in several bacteria, including D. radiodurans. Single crystals were obtained from a recombinant preparation of the catalytic/ATP-binding (CA) domain of D. radiodurans PhoR (79,224) overexpressed in Escherichia coli. The crystals belonged to space group P212121, with unit-cell parameters a = 46.9, b = 81.8, c = 204.6,Å. The crystals contained six molecules in the asymmetric unit. Diffraction data were collected to 2.4,Å resolution on beamline ID23-2 of the European Synchrotron Radiation Facility. [source] Changes associated with the development of resistance to imatinib (STI571) in two leukemia cell lines expressing p210 Bcr/Abl protein,CANCER, Issue 7 2004Barbara Scappini M.D. Abstract BACKGROUND Although various mechanisms have been recognized as being associated with the development of resistance to imatinib mesylate in vitro and in clinical situations, their relative significance and contributions remain poorly understood, as is the sequence of events leading to the selection of the resistant phenotype. Experimental in vitro systems involving well defined cell lines and conditions can be used to some advantage to answer specific questions and to develop in vitro models of imatinib resistance that would reflect its potential heterogeneity. METHODS Two cell lines, KBM5 and KBM7, which expressed p210 Bcr/Abl and which differed in their inherent sensitivity to imatinib, the number of copies of the BCR/ABL fusion gene, and the activation of apoptotic pathways, were grown in vitro in the presence of increasing concentrations of imatinib. The resistant cells were analyzed for cell cycle progression, apoptotic response after exposure to imatinib, expression of Bcr/Abl, tyrosine kinase activity, and the presence of mutations within the adenosine triphosphate (ATP) coding domain of BCR/ABL. At various levels of resistance, the cells were transferred into drug-free media, and the stability of the resistant phenotype was determined in the absence of the drug. RESULTS In KBM7 cells, the development of resistance was characterized by loss of apoptotic response to the drug, amplification of BCR/ABL, increased levels of expression of p210 Bcr/Abl, and decreased inhibition of Bcr/Abl tyrosine kinase (TK) activity by imatinib. No mutations within the ATP-binding domain of Bcr/Abl were identified, and resistance remained stable in the absence of the drug. In KBM5 cells, which previously were found to be characterized by the acquisition of a single C-T mutation at ABL nucleotide 944 (T315I) at high levels of resistance, this same mutation was detected at an intermediate level, but not at a low level, of resistance. The response of KBM5 cells to imatinib was characterized by a low level of apoptotic response, a marginal increase in BCR/ABL copy number, a modest increase in p210 expression, and a highly imatinib-resistant Bcr/Abl TK. Partial reversal of resistance was observed in highly resistant KBM5-STI571R1.0 cells, which continued to display the C-T mutation. In KBM5 cells with an intermediate level of resistance, the T315I mutation was no longer detectable upon their reversal to the sensitive phenotype. CONCLUSIONS BCR/ABL amplification with subsequent overexpression of Bcr/Abl protein, loss of apoptotic response, or point mutation of the ATP-binding site of BCR/ABL was associated alternatively with the acquisition of the resistant phenotype, supporting the notion that multiple mechanisms are involved in the induction of resistance to imatinib. The initial number of BCR/ABL copies itself was not related directly to the degree of resistance. The reversibility of the resistance may be complete, partial, or irreversible, depending on the mechanism(s) involved and the degree of resistance. Both cell lines serve as models for further elucidation of various aspects of imatinib-resistance mechanisms. Cancer 2004;100:1459,71. © 2004 American Cancer Society. [source] Roles of the two ClpC ATP binding sites in the regulation of competence and the stress responseMOLECULAR MICROBIOLOGY, Issue 3 2001Kürsad Turgay MecA targets the competence transcription factor ComK to ClpC. As a consequence, this factor is degraded by the ClpC/ClpP protease. ClpC is a member of the Clp/HSP100 family of ATPases and possesses two ATP binding sites. We have individually modified the Walker A motifs of these two sites and have also deleted a putative substrate recognition domain of ClpC at the C-terminus. The effects of these mutations were studied in vitro and in vivo. Deletion of the C-terminal domain resulted in a decreased binding affinity for MecA, a decreased ATPase activity in response to MecA addition and decreased degradative activity in vitro. In vivo, this deletion resulted in a failure to degrade ComK and in a decrease in thermal resistance for growth. Mutation of the N-terminal Walker A box (K214Q) caused a drastically decreased ATPase activity in vitro, but did not interfere with MecA binding. In vivo, this mutation had no effect on thermal resistance, but had a clpC null phenotype with respect to competence. Mutation of the C-terminal Walker A motif (K551Q) caused essentially the reverse phenotype both in vivo and in vitro. Although binding to MecA was only moderately impaired with 2 mM ATP, this mutant protein displayed no response to 0.2 mM ATP, unlike the wild-type ClpC and the K214Q mutant protein. The ATPase activity of the K551Q mutant protein, induced by the addition of MecA plus ComS, was decreased about 10-fold but was not eliminated. In vivo, the K551Q mutation showed a partial defect with respect to competence and a profound loss of thermal resistance. Sporulation was reduced drastically by the K551Q and less so by the K214Q mutation, but remained unaffected by deletion of the C-terminal domain. Although the evidence suggests that the functions of the two ATP-binding domains overlap, it appears that the N-terminal nucleotide-binding domain of ClpC is particularly concerned with MecA-related functions, whereas the C-terminal domain plays a more general role in the activities of ClpC. [source] Antigenic group II chaperonin in Methanobrevibacter oralis may cross-react with human chaperonin CCTMOLECULAR ORAL MICROBIOLOGY, Issue 2 2010K. Yamabe Summary Methanobrevibacter oralis is an archaeal species frequently isolated from sites of severe periodontitis. However, its pathogenic roles remain unclear. Here, we aimed to isolate group II chaperonin from M. oralis and examine its antigenicity. The genes encoding two chaperonin subunits (Cpn-1 and Cpn-2) were cloned from M. oralis using polymerase chain reaction and genome walking procedures. Recombinant proteins Cpn-1 and Cpn-2 were generated, and the reactivities of sera from patients with periodontitis were examined by Western immunoblotting. The open reading frames of Cpn-1 and Cpn-2 genes consisted of 1641 and 1614 base pairs, respectively. Putative ATP-binding domains conserved among the chaperonin family were observed in both genes. The deduced amino acid sequences of the two genes showed 28.8,40.0% identity to each of the subunits of human CCT (CCT1,8). Thirty and 29 of 36 patients' sera reacted with the recombinant Cpn-1 and recombinant Cpn-2, respectively. Western immunoblotting using antiserum against human CCT subunits indicated that anti-CCT3 and anti-CCT8 antibodies recognized recombinant Cpn-1. In addition, anti-CCT1, CCT3, CCT6, and CCT8 antibodies recognized an antigen of approximately 60 kDa in M. oralis. The results suggested that the chaperonin subunits of M. oralis were antigenic molecules that were recognized by periodontitis patients and that may cross-react with human chaperonin CCT. [source] | |||||||||||||