Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

The putative RNA helicases of the DEAD-box protein family are involved in pre-mRNA splicing, rRNA maturation, ribosome assembly, and translation. Members of this protein family have been identified in organisms from Escherichia coli to humans, but except for the translation initiation factor 4A, there have been no reports on the characterization of other DEAD-box proteins from plants. Here we report on a novel member of the DEAD-box protein family, the plant RNA helicase 75 (PRH75). PRH75 is localized in the nucleus and contains two domains for RNA binding. One is located at the C terminus and is similar to RGG RNA-binding domains of nucleus-localized RNA-binding proteins. The other one is located between amino acids 308 and 622, a region containing the conserved motif VI characteristic of DEAD-box proteins and known as the RNA-binding site of eIF-4A. The N-terminal 81 amino acids are sufficient for nuclear targeting of the protein. Northern and Western blot analyses show that PRH75 is mainly expressed in young and rapidly developing tissues. The purified recombinant PRH75 has a weak ATPase activity which is barely stimulated by RNA ligands. The fractionation of spinach whole-cell extracts by glycerol gradient centrifugation and gel filtration on a Superdex 200 column shows that the protein exists in a complex of about 500 kDa. Possible biological functions of PRH75 as well as structure-function relationships in the context of its modular primary structure are discussed.
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PMID:PRH75, a new nucleus-localized member of the DEAD-box protein family from higher plants. 912 76

A gonadotropin-regulated testicular RNA helicase (GRTH) was identified and characterized. GRTH cloned from rat Leydig cell, mouse testis, and human testis cDNA libraries is a novel member of the DEAD-box protein family. GRTH is transcriptionally up-regulated by chorionic gonadotropin via cyclic AMP-induced androgen formation in the Leydig cell. It has ATPase and RNA helicase activities and increases translation in vitro. This helicase is highly expressed in rat, mouse, and human testes and weakly expressed in the pituitary and hypothalamus. GRTH is produced in both somatic (Leydig cells) and germinal (meiotic spermatocytes and round haploid spermatids) cells and is developmentally regulated. GRTH predominantly localized in the cytoplasm may function as a translational activator. This novel helicase could be relevant to the control of steroidogenesis and the paracrine regulation of androgen-dependent spermatogenesis in the testis.
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PMID:A novel gonadotropin-regulated testicular RNA helicase. A new member of the dead-box family. 1060 60

DNA helicases play an essential role in all aspects of nucleic acid metabolism, by providing a duplex-unwinding function. This is the first report of the isolation of a cDNA (1.6 kb) clone encoding functional DNA helicase from a plant (pea, Pisum sativum). The deduced amino-acid sequence has eight conserved helicase motifs of the DEAD-box protein family. It is a unique member of this family, containing DESD and SRT motifs instead of DEAD/H and SAT. The encoded 45.5 kDa protein has been overexpressed in bacteria and purified to homogeneity. The purified protein contains ATP-dependent DNA and RNA helicase, DNA-dependent ATPase, and ATP-binding activities. The protein sequence contains striking homology with eIF-4A, which has not so far been reported as DNA helicase. The antibodies against pea helicase inhibit in vitro translation. The gene is expressed as 1.6 kb mRNA in different organs of pea. The enzyme is localized in the nucleus and cytosol, and unwinds DNA in the 3' to 5' direction. The pea helicase interacts with pea topoisomerase I protein and stimulates its activity. These results suggest that pea DNA helicase could be an important multifunctional protein involved in protein synthesis, maintaining the basic activities of the cell, and in upregulation of topoisomerase I activity. The discovery of such a protein with intrinsic multiple activity should make an important contribution to our better understanding of DNA and RNA transactions in plants.
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PMID:A DNA helicase from Pisum sativum is homologous to translation initiation factor and stimulates topoisomerase I activity. 1106 96

RNA helicase II/Gu (RH-II/Gu) is a nucleolar DEAD-box protein that unwinds double-stranded RNA and introduces secondary structure to a single-stranded RNA. We recently identified its paralogue, RH-II/Gu(beta), in contrast to the original RH-II/Gu(alpha). Their similar intron-exon structures on chromosome 10 suggest gene duplication. To determine functional differences, their expression, localization, and enzymatic activities were compared. RH-II/Gu(alpha) is expressed two- to threefold more than RH-II/Gu(beta) in most tissues. Both proteins localize to nucleoli, suggesting roles in ribosomal RNA production, but RH-II/Gu(beta) also localizes to nuclear speckles containing splicing factor SC35, suggesting possible involvement in pre-mRNA splicing. The C-terminus responsible for nuclear speckle localization of RH-II/Gu(beta) contains an arginine-serine-rich domain present in some RNA splicing proteins. In vitro assays show weaker ATPase and RNA helicase activities of RH-II/Gu(beta). RH-II/Gu(alpha) unwinds RNA substrate with a 21- or 34-nt duplex and 5' overhangs, but RH-II/Gu(beta) unwinds only the shorter duplex. Although RH-II/Gu(beta) has no RNA folding activity, it catalyzes formation of an RNA complex with unidentified structure, which is not observed when assayed with a mixture of the two enzymes. Instead, the presence of RH-II/Gu(beta) stimulates RH-II/Gu(alpha) unwinding activity. Our data suggest distinct and complex regulation of expression of the two paralogues with nonredundant gene products.
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PMID:Expression, cellular localization, and enzymatic activities of RNA helicase II/Gu(beta). 1202 55

Gonadotropin-regulated testicular RNA helicase (GRTH) is a novel DEAD-box protein with ATPase and RNA helicase activities. GRTH gene transcription is stimulated by human chorionic gonadotropin (hCG) via cyclic AMP-induced androgen formation in testicular Leydig cells. In this study, immunocytochemical and Western analyses identified GRTH as a developmentally regulated protein in Leydig cells and in germ cells (pachytene spermatocytes and round spermatids) of the rat testis. Three ATGs with the potential for generation of multiple protein species were identified. Germ cells primarily utilized the 1st ATG codon (+1) and contained major proteins of 61/56 kDa, whereas Leydig cells utilized preferentially the 2nd ATG codon (+ 343) with expression of 48/43 kDa species. A 3rd ATG was weakly utilized and yielded a 33-kDa protein only in germ cells. The increase in GRTH 43-kDa protein in Leydig cells caused by hCG treatment was prevented by the androgen receptor antagonist, flutamide. In round spermatids, hCG caused a significant decrease of 61 kDa species and an induction 48/43 kDa species, whereas no changes were observed in pachytene spermatocytes. Reversal of this hormone-induced switch of expression by flutamide indicated a role of androgen in utilization of the 2nd ATG. These studies have demonstrated a cell-specific and hormone-dependent alternative usage of ATG codons in the testis. They have also revealed that the androgen-dependent transcription of GRTH expression in Leydig cells is accompanied by a marked increase of 43-kDa species. The findings indicate that expression of GRTH proteins is regulated by gonadotropin/androgen at the translational level.
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PMID:Cell-specific and hormone-regulated expression of gonadotropin-regulated testicular RNA helicase gene (GRTH/Ddx25) resulting from alternative utilization of translation initiation codons in the rat testis. 1273 86

The gonadotropin-regulated testicular RNA helicase (GRTH/DDX25) is a new member of the DEAD-box protein family. Phylogenetic analysis revealed that GRTH is distantly related to other members of the family. GRTH is transcriptionally up-regulated by gonadotropin, displays ATPase and RNA helicase activities, and participates in germ cell development. To understand the regulation of GRTH gene expression, we investigated its structural organization and aspects of basal transcriptional regulation at the promoter domain. The 20-kb mouse GRTH gene contains 12 coding exons and all but one of its conserved helicase motifs are contained within single exons. GRTH is a TATA-less gene with multiple transcriptional start sites (TSS), GC-rich sequences and a promoter located within -205/+63 bp of the gene. Sequences -852/-354 and -501/-354 bp caused 40-60% and >80% inhibition of transcription in expressing and non-expressing cells, respectively. Transcriptional activity was recovered only in expressing cells by the addition of upstream sequences (-1085/-852 bp). Sp1/Sp3 supported basal transcriptional activity in all cell types, while E-box was an activator-binding site only in non-expressing cells. These findings indicate that a differential pattern of transcriptional regulation may be involved in the control of GRTH gene expression in a cell-specific manner.
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PMID:Genomic organization and transcriptional analysis of gonadotropin-regulated testicular RNA helicase--GRTH/DDX25 gene. 1509 94

The yeast DEAD-box protein Has1p is required for the maturation of 18S rRNA, the biogenesis of 40S r-subunits and for the processing of 27S pre-rRNAs during 60S r-subunit biogenesis. We purified recombinant Has1p and characterized its biochemical activities. We show that Has1p is an RNA-dependent ATPase in vitro and that it is able to unwind RNA/DNA duplexes in an ATP-dependent manner. We also report a mutational analysis of the conserved residues in motif I (86AKTGSGKT93), motif III (228SAT230) and motif VI (375HRVGRTARG383). The in vivo lethal K92A substitution in motif I abolishes ATPase activity in vitro. The mutations S228A and T230A partially dissociate ATPase and helicase activities, and they have cold-sensitive and lethal growth phenotypes, respectively. The H375E substitution in motif VI significantly decreased helicase but not ATPase activity and was lethal in vivo. These results suggest that both ATPase and unwinding activities are required in vivo. Has1p possesses a Walker A-like motif downstream of motif VI (383GTKGKGKS390). K389A substitution in this motif significantly increases the Has1p activity in vitro, which indicates it potentially plays a role as a negative regulator. Finally, rRNAs and poly(A) RNA serve as the best stimulators of the ATPase activity of Has1p among the tested RNAs.
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PMID:Characterization of the ATPase and unwinding activities of the yeast DEAD-box protein Has1p and the analysis of the roles of the conserved motifs. 1571 99

Helicases are ubiquitous molecular motor proteins that play important role in maintaining the genome integrity and thus involved in plant growth and development. Here, we report the cloning of cDNA (1.64 kb) and genomic DNA (2.2 kb) of cold stress-induced pea DNA helicase 47 (PDH47) and characterization of its encoded protein. It belongs to DEAD-box protein family and shows striking identity (93%) with tobacco eIF4A. The transcript was induced under cold (4 degrees C) stress. The purified PDH47 protein (47 kDa) contains ATP-/Mg2+-dependent DNA unwinding as well as DNA-/Mg2+-dependent ATPase activities. The ATPase activity of PDH47 is stimulated more by ssDNA as compared to dsDNA and RNA. The activities of PDH47 are inhibited by various DNA-interacting ligands such as nogalamycin, daunorubicin, ethidium bromide, mitoxantrone, actinomycin, and cisplatin with apparent Ki values ranging from 0.5 to 8.0 microM. Interestingly, netropsin and distamycin inhibited the helicase but not the ATPase activity. The inhibition might be due to the intercalation of inhibitors into duplex DNA, which can impede the translocation of the PDH47. This study should help in our better understanding of cold stress signaling and mechanism of DNA unwinding in plants.
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PMID:Cold stress-induced pea DNA helicase 47 is homologous to eIF4A and inhibited by DNA-interacting ligands. 1600 26

The multiprotein exon junction complex (EJC) is assembled on mRNAs as a consequence of splicing. EJC core components maintain a stable grip on mRNAs even as the overall EJC protein composition evolves while mRNAs travel to the cytoplasm. Here we show that recombinant EJC subunits MLN51, MAGOH and Y14, together with the DEAD-box protein eIF4AIII bound to ATP, are necessary and sufficient to form a highly stable complex on single-stranded RNA. Cross-linking and RNase protection studies indicate that this recombinant complex recapitulates the EJC core. The stable association of the recombinant EJC core with RNA is maintained by inhibition of eIF4AIII ATPase activity by MAGOH-Y14. We elucidate the modalities of EJC binding to RNA and provide the first example of how cellular machineries may use RNA helicases to clamp several proteins onto RNA in stable and sequence-independent manners.
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PMID:The exon junction core complex is locked onto RNA by inhibition of eIF4AIII ATPase activity. 1617 Mar 25

RNA helicases of the DEAD-box protein family have been shown to participate in every aspect of RNA metabolism. They are present in most organisms where they work as RNA helicases or RNPases. The properties of these enzymes in vivo remains poorly described, however some were extensively characterized in vitro, and the solved crystal structures of a few are now available. Taken together, this information gives insight into the regulation of ATP and RNA binding as well as in the ATPase and helicase activities. This review will focus on the description of the molecular characteristics of members of the DEAD-box protein family and on the enzymatic activities they possess.
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PMID:The DEAD-box protein family of RNA helicases. 1633 53


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