scholarly journals A minimal region in the NTPase/helicase domain of the TGBp1 plant virus movement protein is responsible for ATPase activity and cooperative RNA binding

2006 ◽  
Vol 87 (10) ◽  
pp. 3087-3095 ◽  
Author(s):  
Anna D. Leshchiner ◽  
Andrey G. Solovyev ◽  
Sergey Yu. Morozov ◽  
Natalia O. Kalinina
Keyword(s):  
Amino Acid ◽  
Atpase Activity ◽  
Amino Acid Residue ◽  
Plant Virus ◽  
Rna Binding ◽  
Triple Gene Block ◽  
Basic Amino Acid ◽  
Helicase Domain ◽  
Basic Amino Acid Residue ◽  
Conserved Sequence

The TGBp1 protein, encoded in the genomes of a number of plant virus genera as the first gene of the ‘triple gene block’, possesses an NTPase/helicase domain characterized by seven conserved sequence motifs. It has been shown that the TGBp1 NTPase/helicase domain exhibits NTPase, RNA helicase and RNA-binding activities. In this paper, we have analysed a series of deletion and point mutants in the TGBp1 proteins encoded by Potato virus X (PVX, genus Potexvirus) and Poa semilatent virus (PSLV, genus Hordeivirus) to map functional regions responsible for their biochemical activities in vitro. It was found that, in both PVX and PSLV, the N-terminal part of the TGBp1 NTPase/helicase domain comprising conserved motifs I, Ia and II was sufficient for ATP hydrolysis, RNA binding and homologous protein–protein interactions. Point mutations in a single conserved basic amino acid residue upstream of motif I had little effect on the activities of C-terminally truncated mutants of both TGBp1 proteins. However, when introduced into the full-length NTPase/helicase domains, these mutations caused a substantial decrease in the ATPase activity of the protein, suggesting that the conserved basic amino acid residue upstream of motif I was required to maintain a reaction-competent conformation of the TGBp1 ATPase active site.

scholarly journals Structure-Based Mutational Analysis of the Hepatitis C Virus NS3 Helicase

2001 ◽  
Vol 75 (17) ◽  
pp. 8289-8297 ◽  
Author(s):  
Chun-Ling Tai ◽  
Wen-Ching Pan ◽  
Shwu-Huey Liaw ◽  
Ueng-Cheng Yang ◽  
Lih-Hwa Hwang ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Atpase Activity ◽  
Rna Binding ◽  
Mutational Analysis ◽  
Nonstructural Protein ◽  
Rna Helicase ◽  
Helicase Domain ◽  
Helicase Activity ◽  
Conserved Sequence

ABSTRACT The carboxyl terminus of the hepatitis C virus (HCV) nonstructural protein 3 (NS3) possesses ATP-dependent RNA helicase activity. Based on the conserved sequence motifs and the crystal structures of the helicase domain, 17 mutants of the HCV NS3 helicase were generated. The ATP hydrolysis, RNA binding, and RNA unwinding activities of the mutant proteins were examined in vitro to determine the functional role of the mutated residues. The data revealed that Lys-210 in the Walker A motif and Asp-290, Glu-291, and His-293 in the Walker B motif were crucial to ATPase activity and that Thr-322 and Thr-324 in motif III and Arg-461 in motif VI significantly influenced ATPase activity. When the pairing between His-293 and Gln-460, referred to as gatekeepers, was replaced with the Asp-293/His-460 pair, which makes the NS3 helicase more like the DEAD helicase subgroup, ATPase activity was not restored. It thus indicated that the whole microenvironment surrounding the gatekeepers, rather than the residues per se, was important to the enzymatic activities. Arg-461 and Trp-501 are important residues for RNA binding, while Val-432 may only play a coadjutant role. The data demonstrated that RNA helicase activity was possibly abolished by the loss of ATPase activity or by reduced RNA binding activity. Nevertheless, a low threshold level of ATPase activity was found sufficient for helicase activity. Results in this study provide a valuable reference for efforts under way to develop anti-HCV therapeutic drugs targeting NS3.

scholarly journals Identification and Analysis of Novel Amino-Acid Sequence Repeats inBacillus anthracisstr.AmesProteome Using Computational Tools

2007 ◽  
Vol 2007 ◽  
pp. 1-23 ◽  
Author(s):  
G. R. Hemalatha ◽  
D. Satyanarayana Rao ◽  
L. Guruprasad
Keyword(s):  
Amino Acid ◽  
Amino Acid Residue ◽  
Protein Sequence ◽  
Amino Acid Residues ◽  
Sequence Motifs ◽  
Computational Tools ◽  
Conserved Sequence ◽  
Conserved Sequence Motifs ◽  
Multiple Copies ◽  
Domain 3

We have identified four repeats and ten domains that are novel in proteins encoded by theBacillus anthracisstr.Amesproteome using automated in silico methods. A “repeat” corresponds to a region comprising less than 55-amino-acid residues that occur more than once in the protein sequence and sometimes present in tandem. A “domain” corresponds to a conserved region with greater than 55-amino-acid residues and may be present as single or multiple copies in the protein sequence. These correspond to (1) 57-amino-acid-residue PxV domain, (2) 122-amino-acid-residue FxF domain, (3) 111-amino-acid-residue YEFF domain, (4) 109-amino-acid-residue IMxxH domain, (5) 103-amino-acid-residue VxxT domain, (6) 84-amino-acid-residue ExW domain, (7) 104-amino-acid-residue NTGFIG domain, (8) 36-amino-acid-residue NxGK repeat, (9) 95-amino-acid-residue VYV domain, (10) 75-amino-acid-residue KEWE domain, (11) 59-amino-acid-residue AFL domain, (12) 53-amino-acid-residue RIDVK repeat, (13) (a) 41-amino-acid-residue AGQF repeat and (b) 42-amino-acid-residue GSAL repeat. A repeat or domain type is characterized by specific conserved sequence motifs. We discuss the presence of these repeats and domains in proteins from other genomes and their probable secondary structure.

scholarly journals Structure-Based Mutagenesis Study of Hepatitis C Virus NS3 Helicase

1999 ◽  
Vol 73 (10) ◽  
pp. 8798-8807 ◽  
Author(s):  
Chao Lin ◽  
Joseph L. Kim
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Nucleic Acid ◽  
Atpase Activity ◽  
Rna Binding ◽  
Crystallographic Structure ◽  
Binary Complex ◽  
Helicase Domain ◽  
Wild Type ◽  
Ns3 Protein

ABSTRACT The NS3 protein of hepatitis C virus (HCV) is a bifunctional protein containing a serine protease in the N-terminal one-third, which is stimulated upon binding of the NS4A cofactor, and an RNA helicase in the C-terminal two-thirds. In this study, a C-terminal hexahistidine-tagged helicase domain of the HCV NS3 protein was expressed in Escherichia coli and purified to homogeneity by conventional chromatography. The purified HCV helicase domain has a basal ATPase activity, a polynucleotide-stimulated ATPase activity, and a nucleic acid unwinding activity and binds efficiently to single-stranded polynucleotide. Detailed characterization of the purified HCV helicase domain with regard to all four activities is presented. Recently, we published an X-ray crystallographic structure of a binary complex of the HCV helicase with a (dU)8oligonucleotide, in which several conserved residues of the HCV helicase were shown to be involved in interactions between the HCV helicase and oligonucleotide. Here, site-directed mutagenesis was used to elucidate the roles of these residues in helicase function. Four individual mutations, Thr to Ala at position 269, Thr to Ala at position 411, Trp to Leu at position 501, and Trp to Ala at position 501, produced a severe reduction of RNA binding and completely abolished unwinding activity and stimulation of ATPase activity by poly(U), although the basal ATPase activity (activity in the absence of polynucleotide) of these mutants remained intact. Alanine substitution at Ser-231 or Ser-370 resulted in enzymes that were indistinguishable from wild-type HCV helicase with regard to all four activities. A mutant bearing Phe at Trp-501 showed wild-type levels of basal ATPase, unwinding activity, and single-stranded RNA binding activity. Interestingly, ATPase activity of this mutant became less responsive to stimulation by poly(U) but not to stimulation by other polynucleotides, such as poly(C). Given the conservation of some of these residues in other DNA and RNA helicases, their role in the mechanism of unwinding of double-stranded nucleic acid is discussed.

scholarly journals Structural insights into RNA recognition by the Chikungunya virus nsP2 helicase

2019 ◽  
Vol 116 (19) ◽  
pp. 9558-9567 ◽  
Author(s):  
Yee-Song Law ◽  
Age Utt ◽  
Yaw Bia Tan ◽  
Jie Zheng ◽  
Sainan Wang ◽  
...  
Keyword(s):  
Atpase Activity ◽  
Chikungunya Virus ◽  
Rna Binding ◽  
Nonstructural Protein ◽  
Rna Helicase ◽  
Viral Rna ◽  
Helicase Domain ◽  
Stacking Interactions ◽  
Adaptive Mutations ◽  
Rna Backbone

Chikungunya virus (CHIKV) is transmitted to humans through mosquitoes and causes Chikungunya fever. Nonstructural protein 2 (nsP2) exhibits the protease and RNA helicase activities that are required for viral RNA replication and transcription. Unlike for the C-terminal protease, the structure of the N-terminal RNA helicase (nsP2h) has not been determined. Here, we report the crystal structure of the nsP2h bound to the conserved 3′-end 14 nucleotides of the CHIKV genome and the nonhydrolyzable transition-state nucleotide analog ADP-AlF4. Overall, the structural analysis revealed that nsP2h adopts a uniquely folded N-terminal domain followed by a superfamily 1 RNA helicase fold. The conserved helicase motifs establish polar contacts with the RNA backbone. There are three hydrophobic residues (Y161, F164, and F287) which form stacking interactions with RNA bases and thereby bend the RNA backbone. An F287A substitution that disrupted these stacking interactions increased the basal ATPase activity but decreased the RNA binding affinity. Furthermore, the F287A substitution reduced viral infectivity by attenuating subgenomic RNA synthesis. Replication of the mutant virus was restored by pseudoreversion (A287V) or adaptive mutations in the RecA2 helicase domain (T358S or V410I). Y161A and/or F164A substitutions, which were designed to disrupt the interactions with the RNA molecule, did not affect the ATPase activity but completely abolished the replication and transcription of viral RNA and the infectivity of CHIKV. Our study sheds light on the roles of the RNA helicase region in viral replication and provides insights that might be applicable to alphaviruses and other RNA viruses in general.

Mutational analysis of hepatitis C virus NS3-associated helicase

Microbiology ◽  
2000 ◽  
Vol 81 (7) ◽  
pp. 1649-1658 ◽  
Author(s):  
Chantal Paolini ◽  
Armin Lahm ◽  
Raffaele De Francesco ◽  
Paola Gallinari
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Amino Acid ◽  
Atpase Activity ◽  
Mutational Analysis ◽  
Nonstructural Protein ◽  
Binding Capacity ◽  
Molecular Model ◽  
Helicase Domain ◽  
Amino Acid Residues

Nonstructural protein 3 (NS3) of hepatitis C virus contains a bipartite structure consisting of an N-terminal serine protease and a C-terminal DEXH box helicase. To investigate the roles of individual amino acid residues in the overall mechanism of unwinding, a mutational–functional analysis was performed based on a molecular model of the NS3 helicase domain bound to ssDNA, which has largely been confirmed by a recently published crystal structure of the NS3 helicase–ssDNA complex. Three full-length mutated NS3 proteins containing Tyr(392)Ala, Val(432)Gly and Trp(501)Ala single substitutions, respectively, together with a Tyr(392)Ala/Trp(501)Ala double-substituted protein were expressed in Escherichia coli and purified to homogeneity. All individually mutated forms showed a reduction in duplex unwinding activity, single-stranded polynucleotide binding capacity and polynucleotide-stimulated ATPase activity compared to wild-type, though to different extents. Simultaneous replacement of both Tyr392 and Trp501 with Ala completely abolished all these enzymatic functions. On the other hand, the introduced amino acid substitutions had no influence on NS3 intrinsic ATPase activity and proteolytic efficiency. The results obtained with Trp(501)Ala and Val(432)Gly single-substituted enzymes are in agreement with a recently proposed model for NS3 unwinding activity. The mutant phenotype of the Tyr(392)Ala and Tyr(392)Ala/Trp(501)Ala enzymes, however, represents a completely novel finding.

scholarly journals Domain organization of the N-terminal portion of hordeivirus movement protein TGBp1

2009 ◽  
Vol 90 (12) ◽  
pp. 3022-3032 ◽  
Author(s):  
Valentin V. Makarov ◽  
Ekaterina N. Rybakova ◽  
Alexander V. Efimov ◽  
Eugene N. Dobrov ◽  
Marina V. Serebryakova ◽  
...  
Keyword(s):  
Secondary Structure ◽  
Molecular Mass ◽  
Rna Binding ◽  
Triple Gene Block ◽  
Plant Viruses ◽  
Protein Domain ◽  
Helicase Domain ◽  
Long Distance ◽  
Genomic Rnas ◽  
Gene Block

Three ‘triple gene block’ proteins known as TGBp1, TGBp2 and TGBp3 are required for cell-to-cell movement of plant viruses belonging to a number of genera including Hordeivirus. Hordeiviral TGBp1 interacts with viral genomic RNAs to form ribonucleoprotein (RNP) complexes competent for translocation between cells through plasmodesmata and over long distances via the phloem. Binding of hordeivirus TGBp1 to RNA involves two protein regions, the C-terminal NTPase/helicase domain and the N-terminal extension region. This study demonstrated that the extension region of hordeivirus TGBp1 consists of two structurally and functionally distinct domains called the N-terminal domain (NTD) and the internal domain (ID). In agreement with secondary structure predictions, analysis of circular dichroism spectra of the isolated NTD and ID demonstrated that the NTD represents a natively unfolded protein domain, whereas the ID has a pronounced secondary structure. Both the NTD and ID were able to bind ssRNA non-specifically. However, whilst the NTD interacted with ssRNA non-cooperatively, the ID bound ssRNA in a cooperative manner. Additionally, both domains bound dsRNA. The NTD and ID formed low-molecular-mass oligomers, whereas the ID also gave rise to high-molecular-mass complexes. The isolated ID was able to interact with both the NTD and the C-terminal NTPase/helicase domain in solution. These data demonstrate that the hordeivirus TGBp1 has three RNA-binding domains and that interaction between these structural units can provide a basis for remodelling of viral RNP complexes at different steps of cell-to-cell and long-distance transport of virus infection.

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