Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.6.1.3 (ATPase)
 65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In bacteria, yeast, and mammals, iron-sulfur (Fe-S) cluster-containing proteins are involved in numerous processes including electron transfer, metabolic reactions, sensing, signaling, and regulation of gene expression. In humans, iron-storage diseases such as X-linked sideroblastic anemia and ataxia are caused by defects in Fe-S cluster availability. The biogenesis of Fe-S clusters involves several pathways, and in bacteria, the SufABCDSE operon has been shown to play a vital role in Fe-S biogenesis and repair during oxidative stress. Although Fe-S proteins play vital roles in plants, Fe-S cluster biogenesis and maintenance and physiological consequences of dysfunctional Fe-S cluster assembly remains obscure. Here we report that Arabidopsis plants deficient for the SufC homolog AtNAP7 show lethality at the globular stage of embryogenesis. AtNAP7 is expressed in developing embryos and in apical, root, and floral meristems and encodes an ATP-binding cassette/ATPase that can partially rescue growth defects in an Escherichia coli SufC mutant during oxidative stress. AtNAP7 is plastid-localized, and mutant embryos contain abnormal developing plastids with disorganized thylakoid structures. We found that AtNAP7 can interact with AtNAP6, a plastidic Arabidopsis SufD homolog, and because Arabidopsis plastids also harbor SufA, SufB, SufS, and SufE homologs, plastids probably contain a complete SUF system. Our results imply that AtNAP7 represents a conserved SufC protein involved in the biogenesis and/or repair of oxidatively damaged Fe-S clusters and suggest an important role for plastidic Fe-S cluster maintenance and repair during Arabidopsis embryogenesis.
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PMID:AtNAP7 is a plastidic SufC-like ATP-binding cassette/ATPase essential for Arabidopsis embryogenesis. 1518 73

Multidrug resistance (MDR)-type transporters mediate the active extrusion of structurally and functionally dissimilar compounds from the cells, thereby rendering cells resistant to a range of drugs. The ydaG and ydbA genes of Lactococcus lactis encode two ATP-binding cassette half-transporters, which both share homology with MDR proteins such as LmrA from L. lactis or the mammalian P-glycoprotein. The ydaG/ydbA genes were cloned and expressed separately and jointly in L. lactis using the nisin-inducible system. When both proteins are co-expressed, several structurally dissimilar drugs such as ethidium, daunomycin, and BCECF-AM are extruded from the cell. YdaG and YdbA could be co-purified as a stable heterodimer. ATPase activity was found to be associated with the YdaG/YdbA heterodimer only and not with the individual subunits. Both the ydaG and ydbA genes are up-regulated in multidrug-resistant L. lactis strains selected for growth in the presence of a variety of toxic compounds. This is the first demonstration of a functional heterodimeric ATP-binding cassette-type MDR transporter.
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PMID:ydaG and ydbA of Lactococcus lactis encode a heterodimeric ATP-binding cassette-type multidrug transporter. 1519 86

Porphyromonas gingivalis, one of the causative agents of adult periodontitis, can invade and survive within host epithelial cells. The molecular mechanisms by which P. gingivalis induces uptake and adapts to an intracellular environment are not fully understood. In this study, we have investigated the genetic responses of P. gingivalis internalized within human gingival epithelial cells (GECs) in order to identify factors involved in invasion and survival. We compared the differential display of arbitrarily PCR-amplified gene transcripts in P. gingivalis recovered from GECs with the display of transcripts in P. gingivalis control cultures. Over 20 potential differentially expressed transcripts were identified. Among these, pepO, encoding an endopeptidase, and genes encoding an ATP-binding cassette (ABC) transporter and a cation-transporting ATPase were upregulated in GECs. To investigate the functionality of these gene products, mutants were generated by insertional inactivation. Compared to the parental strain, mutants of each gene showed a significant reduction in their invasion capabilities. In addition, GEC cytoskeletal responses to the mutants were distinct from those induced by the parent. In contrast, adhesion of the mutant strains to GECs was not affected by lack of expression of the gene products. These results suggest that PepO, a cation-transporting ATPase, and an ABC transporter are required for the intracellular lifestyle of P. gingivalis.
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PMID:Identification of Porphyromonas gingivalis genes specifically expressed in human gingival epithelial cells by using differential display reverse transcription-PCR. 1521 15

The most common cause of cystic fibrosis is misfolding of the cystic fibrosis transmembrane conductance regulator (CFTR) protein because of deletion of residue Phe-508 (DeltaF508). P-glycoprotein (P-gp) is an ideal model protein for studying how mutations disrupt folding of ATP-binding cassette proteins such as CFTR because specific chemical chaperones can be used to correct folding defects. Interactions between the nucleotide binding domains (NBDs) are critical because ATP binds at the interface between the NBDs. Here, we used disulfide cross-linking between cysteines in the Walker A sites and the LSGGQ signature sequences to test whether processing mutations located throughout P-gp disrupted interactions between the NBDs. We found that mutations present in the cytoplasmic loops, transmembrane segments, and linker regions or deletion of Tyr-490 (equivalent to Phe-508 in CFTR) inhibited cross-linking between the NBDs. Deletion of Phe-508 in the P-gp/CFTR chimera also inhibited cross-linking between the NBDs. Cross-linking was restored, however, when the mutants were expressed in the presence of the chemical chaperone cyclosporin A. The "rescued" mutants exhibited drug-stimulated ATPase activity, and cross-linking between the NBDs was inhibited by vanadate trapping of nucleotide. These results together with our previous findings (Loo, T. W., Bartlett, M. C., and Clarke, D. M. (2002) J. Biol. Chem. 277, 27585-27588) indicate that processing mutations disrupt interactions among all four domains. It appears that cross-talk between the cytoplasmic and the transmembrane domains is required for establishment of proper domain-domain interactions that occur during folding of ATP-binding cassette protein transporters.
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PMID:Processing mutations located throughout the human multidrug resistance P-glycoprotein disrupt interactions between the nucleotide binding domains. 1524 15

The transporter associated with antigen processing (TAP) is a key component of the cellular immune system. As a member of the ATP-binding cassette (ABC) superfamily, TAP hydrolyzes ATP to energize the transport of peptides from the cytosol into the lumen of the endoplasmic reticulum. TAP is composed of TAP1 and TAP2, each containing a transmembrane domain and a nucleotide-binding domain (NBD). Here we investigated the role of the ABC signature motif (C-loop) on the functional non-equivalence of the NBDs, which contain a canonical C-loop (LSGGQ) for TAP1 and a degenerate C-loop (LAAGQ) for TAP2. Mutation of the leucine or glycine (LSGGQ) in TAP1 fully abolished peptide transport. However, TAP complexes with equivalent mutations in TAP2 still showed residual peptide transport activity. To elucidate the origin of the asymmetry of the NBDs of TAP, we further examined TAP complexes with exchanged C-loops. Strikingly, the chimera with two canonical C-loops showed the highest transport rate whereas the chimera with two degenerate C-loops had the lowest transport rate, demonstrating that the ABC signature motifs control peptide transport efficiency. All single site mutants and chimeras showed similar activities in peptide or ATP binding, implying that these mutations affect the ATPase activity of TAP. In addition, these results prove that the serine of the C-loop is not essential for TAP function but rather coordinates, together with other residues of the C-loop, the ATP hydrolysis in both nucleotide-binding sites.
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PMID:Functional non-equivalence of ATP-binding cassette signature motifs in the transporter associated with antigen processing (TAP). 1532 97

ATP-binding cassette (ABC) transporters move solutes across membranes and are associated with important diseases, including cystic fibrosis and multi-drug resistance. These molecular machines are energized by their charateristic ABC modules, molecular engines fuelled by ATP hydrolysis. A solution NMR study of a model ABC, Methanococcus jannaschii protein MJ1267, reveals that ADP-Mg binding alters the flexibilities of key ABC motifs and induces allosteric changes in conformational dynamics in the LivG insert, over 30A away from the ATPase active site. (15)N spin relaxation data support a "selected-fit" model for nucleotide binding. Transitions between rigidity and flexibility in key motifs during the ATP hydrolysis cycle may be crucial to mechanochemical energy transduction in ABC transporters. The restriction of correlated protein motions is likely a central mechanism for allosteric communications. Comparison between dynamics data from NMR and X-ray crystallography reveals their overall consistency and complementarity.
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PMID:Dynamics of ATP-binding cassette contribute to allosteric control, nucleotide binding and energy transduction in ABC transporters. 1532 52

The Acinetobacter baumannii type strain, ATCC 19606, secretes acinetobactin, a catechol siderophore highly related to the iron chelator anguibactin produced by the fish pathogen Vibrio anguillarum (Listonella anguillarum). This paper reports the initial characterization of the genes and gene products involved in the acinetobactin-mediated iron-acquisition process. Insertional mutagenesis resulted in the isolation of several derivatives whose ability to grow in medium containing the iron chelator 2,2'-dipyridyl was affected. One of the insertions disrupted a gene encoding a predicted outer-membrane protein, named BauA, highly similar to FatA, the receptor for ferric anguibactin. Immunological relatedness of BauA with FatA was confirmed by Western blot analysis. Another transposon insertion was mapped to a gene encoding a protein highly similar to FatD, the permease component of the anguibactin transport system. Further DNA sequencing and nucleotide sequence analysis revealed that these A. baumannii 19606 genes are part of a polycistronic locus that contains the bauDCEBA ORFs. While the translation products of bauD, -C, -B and -A are highly related to the V. anguillarum FatDCBA iron-transport proteins, the product of bauE is related to the ATPase component of Gram-positive ATP-binding cassette (ABC) transport systems. This entire locus is flanked by genes encoding predicted proteins related to AngU and AngN, V. anguillarum proteins required for the biosynthesis of anguibactin. These protein similarities, as well as the structural similarity of anguibactin and acinetobactin, suggested that these two siderophores could be utilized by both bacterial strains, a possibility that was confirmed by siderophore utilization bioassays. Taken together, these results demonstrate that these pathogens, which cause serious infections in unrelated hosts, express very similar siderophore-mediated iron-acquisition systems.
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PMID:The siderophore-mediated iron acquisition systems of Acinetobacter baumannii ATCC 19606 and Vibrio anguillarum 775 are structurally and functionally related. 1552 53

Several ATP-binding cassette (ABC) transporters can confer multidrug resistance to cancer cells by functioning as energy-dependent efflux pumps. The half-transporter ABCG2 and the widely studied P-glycoprotein (P-gp) are two ABC transporters that, when overexpressed, are capable of extruding a variety of structurally unrelated chemotherapy agents from cells. In this study, we demonstrate that human ABCG2 and P-glycoprotein, despite overlapping substrate specificities, differ in sensitivity to the immunomodulator cyclosporin A. In this study, we used human ABCG2 and human P-gp, each expressed separately in drug-selected MCF-7 sublines and transiently transfected HeLa cells. By flow cytometric analysis using the fluorescent substrates rhodamine 123 and mitoxantrone, we showed that cyclosporin A inhibits P-gp function at low micromolar concentrations, whereas ABCG2 function was unaffected. Furthermore, P-gp, but not ABCG2, was able to transport [3H]cyclosporin A directly in intact cells. We also demonstrated, for the first time, that [125I]iodoarylazidoprazosin, a photoaffinity analog of the substrate prazosin, labels multiple variants of ABCG2 specifically and that this labeling, although competed by some ABCG2 substrates, is unaffected by cyclosporin A. These labeling data also suggest the presence of multiple drug binding sites in ABCG2. In addition, cyclosporin A had no effect on the basal or prazosin-stimulated ATPase activity of ABCG2, whereas both the basal and verapamil-stimulated ATPase activities of P-gp were inhibited markedly. Together, our results suggest that cyclosporin A is neither a substrate nor an inhibitor of the human ABCG2 transporter, under the conditions and concentrations examined.
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PMID:Differential sensitivities of the human ATP-binding cassette transporters ABCG2 and P-glycoprotein to cyclosporin A. 1559 74

Accumulating evidence suggests that several ATP-binding cassette (ABC) transporters mediate the elimination of anticancer drugs from cancer cells and thereby confer drug resistance. SN-38-selected PC-6/SN2-5H human lung carcinoma cells were shown to overexpress ABCG2 with the reduced intracellular accumulation of SN-38, the active metabolite of irinotecan. We have recently demonstrated that plasma membrane vesicles prepared from those cells transported SN-38 in an ATP-dependent manner, and it was suggested that ABCG2 is involved in the active extrusion of SN-38 from cancer cells. In the present study, we have cloned the cDNA of ABCG2 from PC-6/SN2-5H human lung carcinoma cells, expressed ABCG2 in Sf9 insect cells, and characterized its function. Sequence analysis has revealed that the cloned ABCG2 has an arginine at the amino acid position 482, as does the wild type. Expression of the cloned ABCG2 in Sf9 cell membranes was detected by immunoblotting with the BXP-21 antibody. Contrary to our expectation, however, ATPase activity in the cell membranes expressing ABCG2 was stimulated by neither SN-38 nor rhodamine 123. It is suggested that there is a partner protein of ABCG2 required for heterodimer formation to exhibit transport activity toward SN-38.
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PMID:Does ABCG2 need a heterodimer partner? Expression and functional evaluation of ABCG2 (Arg 482)*. 1561 61

The ATPase activity of the ABC (ATP-binding cassette) ATPase domain of the HlyB (haemolysin B) transporter is required for secretion of Escherichia coli haemolysin via the type I pathway. Although ABC transporters are generally presumed to function as dimers, the precise role of dimerization remains unclear. In the present study, we have analysed the HlyB ABC domain, purified separately from the membrane domain, with respect to its activity and capacity to form physically detectable dimers. The ATPase activity of the isolated ABC domain clearly demonstrated positive co-operativity, with a Hill coefficient of 1.7. Furthermore, the activity is (reversibly) inhibited by salt concentrations in the physiological range accompanied by proportionately decreased binding of 8-azido-ATP. Inhibition of activity with increasing salt concentration resulted in a change in flexibility as detected by intrinsic tryptophan fluorescence. Finally, ATPase activity was sensitive towards orthovanadate, with an IC50 of 16 microM, consistent with the presence of transient dimers during ATP hydrolysis. Nevertheless, over a wide range of protein or of NaCl or KCl concentrations, the ABC ATPase was only detected as a monomer, as measured by ultracentrifugation or gel filtration. In contrast, in the absence of salt, the sedimentation velocity determined by analytical ultracentrifugation suggested a rapid equilibrium between monomers and dimers. Small amounts of dimers, but apparently only when stabilized by 8-azido-ATP, were also detected by gel filtration, even in the presence of salt. These data are consistent with the fact that monomers can interact at least transiently and are the important species during ATP hydrolysis.
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PMID:Positive co-operative activity and dimerization of the isolated ABC ATPase domain of HlyB from Escherichia coli. 1563 83


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