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Krasnov VP, Andronova VL, Belyavsky AV, Borisevich SS, Galegov GA, Kandarakov OF, Gruzdev DA, Vozdvizhenskaya OA, Levit GL. Large Subunit of the Human Herpes Simplex Virus Terminase as a Promising Target in Design of Anti-Herpesvirus Agents. Molecules 2023; 28:7375. [PMID: 37959793 PMCID: PMC10649544 DOI: 10.3390/molecules28217375] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Revised: 10/19/2023] [Accepted: 10/23/2023] [Indexed: 11/15/2023] Open
Abstract
Herpes simplex virus type 1 (HSV-1) is an extremely widespread pathogen characterized by recurrent infections. HSV-1 most commonly causes painful blisters or sores around the mouth or on the genitals, but it can also cause keratitis or, rarely, encephalitis. First-line and second-line antiviral drugs used to treat HSV infections, acyclovir and related compounds, as well as foscarnet and cidofovir, selectively inhibit herpesvirus DNA polymerase (DNA-pol). It has been previously found that (S)-4-[6-(purin-6-yl)aminohexanoyl]-7,8-difluoro-3,4-dihydro-3-methyl-2H-[1,4]benzoxazine (compound 1) exhibits selective anti-herpesvirus activity against HSV-1 in cell culture, including acyclovir-resistant mutants, so we consider it as a lead compound. In this work, the selection of HSV-1 clones resistant to the lead compound was carried out. High-throughput sequencing of resistant clones and reference HSV-1/L2 parent strain was performed to identify the genetic determinants of the virus's resistance to the lead compound. We identified a candidate mutation presumably associated with resistance to the virus, namely the T321I mutation in the UL15 gene encoding the large terminase subunit. Molecular modeling was used to evaluate the affinity and dynamics of the lead compound binding to the putative terminase binding site. The results obtained suggest that the lead compound, by binding to pUL15, affects the terminase complex. pUL15, which is directly involved in the processing and packaging of viral DNA, is one of the crucial components of the HSV terminase complex. The loss of its functional activity leads to disruption of the formation of mature virions, so it represents a promising drug target. The discovery of anti-herpesvirus agents that affect biotargets other than DNA polymerase will expand our possibilities of targeting HSV infections, including those resistant to baseline drugs.
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Affiliation(s)
- Victor P. Krasnov
- Postovsky Institute of Organic Synthesis, Russian Academy of Sciences (Ural Branch), Ekaterinburg 620108, Russia; (D.A.G.); (O.A.V.); (G.L.L.)
| | - Valeriya L. Andronova
- Gamaleya National Research Center for Epidemiology and Microbiology, Ministry of Health of the Russian Federation, Moscow 123098, Russia; (V.L.A.); (G.A.G.)
| | - Alexander V. Belyavsky
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow 119991, Russia; (A.V.B.); (O.F.K.)
| | | | - George A. Galegov
- Gamaleya National Research Center for Epidemiology and Microbiology, Ministry of Health of the Russian Federation, Moscow 123098, Russia; (V.L.A.); (G.A.G.)
| | - Oleg F. Kandarakov
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow 119991, Russia; (A.V.B.); (O.F.K.)
| | - Dmitry A. Gruzdev
- Postovsky Institute of Organic Synthesis, Russian Academy of Sciences (Ural Branch), Ekaterinburg 620108, Russia; (D.A.G.); (O.A.V.); (G.L.L.)
| | - Olga A. Vozdvizhenskaya
- Postovsky Institute of Organic Synthesis, Russian Academy of Sciences (Ural Branch), Ekaterinburg 620108, Russia; (D.A.G.); (O.A.V.); (G.L.L.)
| | - Galina L. Levit
- Postovsky Institute of Organic Synthesis, Russian Academy of Sciences (Ural Branch), Ekaterinburg 620108, Russia; (D.A.G.); (O.A.V.); (G.L.L.)
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Meanwell NA. Sub-stoichiometric Modulation of Viral Targets-Potent Antiviral Agents That Exploit Target Vulnerability. ACS Med Chem Lett 2023; 14:1021-1030. [PMID: 37583823 PMCID: PMC10424314 DOI: 10.1021/acsmedchemlett.3c00279] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Accepted: 06/30/2023] [Indexed: 08/17/2023] Open
Abstract
The modulation of oligomeric viral targets at sub-stoichiometric ratios of drug to target has been advocated for its efficacy and potency, but there are only a limited number of documented examples. In this Viewpoint, we summarize the invention of the HIV-1 maturation inhibitor fipravirimat and discuss the emerging details around the mode of action of this class of drug that reflects inhibition of a protein composed of 1,300-1,600 monomers that interact in a cooperative fashion. Similarly, the HCV NS5A inhibitor daclatasvir has been shown to act in a highly sub-stoichiometric fashion, inhibiting viral replication at concentrations that are ∼23,500 lower than that of the protein target.
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Weitao T, Grandinetti G, Guo P. Revolving ATPase motors as asymmetrical hexamers in translocating lengthy dsDNA via conformational changes and electrostatic interactions in phi29, T7, herpesvirus, mimivirus, E. coli, and Streptomyces. EXPLORATION (BEIJING, CHINA) 2023; 3:20210056. [PMID: 37324034 PMCID: PMC10191066 DOI: 10.1002/exp.20210056] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/17/2021] [Accepted: 04/28/2022] [Indexed: 06/17/2023]
Abstract
Investigations of the parallel architectures of biomotors in both prokaryotic and eukaryotic systems suggest a similar revolving mechanism in the use of ATP to drive translocation of the lengthy double-stranded (ds)DNA genomes. This mechanism is exemplified by the dsDNA packaging motor of bacteriophage phi29 that operates through revolving but not rotating dsDNA to "Push through a one-way valve". This unique and novel revolving mechanism discovered in phi29 DNA packaging motor was recently reported in other systems including the dsDNA packaging motor of herpesvirus, the dsDNA ejecting motor of bacteriophage T7, the plasmid conjugation machine TraB in Streptomyces, the dsDNA translocase FtsK of gram-negative bacteria, and the genome-packaging motor in mimivirus. These motors exhibit an asymmetrical hexameric structure for transporting the genome via an inch-worm sequential action. This review intends to delineate the revolving mechanism from a perspective of conformational changes and electrostatic interactions. In phi29, the positively charged residues Arg-Lys-Arg in the N-terminus of the connector bind the negatively charged interlocking domain of pRNA. ATP binding to an ATPase subunit induces the closed conformation of the ATPase. The ATPase associates with an adjacent subunit to form a dimer facilitated by the positively charged arginine finger. The ATP-binding induces a positive charging on its DNA binding surface via an allostery mechanism and thus the higher affinity for the negatively charged dsDNA. ATP hydrolysis induces an expanded conformation of the ATPase with a lower affinity for dsDNA due to the change of the surface charge, but the (ADP+Pi)-bound subunit in the dimer undergoes a conformational change that repels dsDNA. The positively charged lysine rings of the connector attract dsDNA stepwise and periodically to keep its revolving motion along the channel wall, thus maintaining the one-way translocation of dsDNA without reversal and sliding out. The finding of the presence of the asymmetrical hexameric architectures of many ATPases that use the revolving mechanism may provide insights into the understanding of translocation of the gigantic genomes including chromosomes in complicated systems without coiling and tangling to speed up dsDNA translocation and save energy.
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Affiliation(s)
- Tao Weitao
- UT Southwestern Medical CenterCenter for the Genetics of Host DefenseDallasTXUSA
- College of Science and MathematicsSouthwest Baptist UniversityBolivarMOUSA
| | - Giovanna Grandinetti
- Center for Electron Microscopy and AnalysisThe Ohio State UniversityColumbusOHUSA
| | - Peixuan Guo
- Center for RNA Nanobiotechnology and NanomedicineDivision of Pharmaceutics and Pharmacology, College of PharmacyDorothy M. Davis Heart and Lung Research Institute, James Comprehensive Cancer Center, College of MedicineThe Ohio State UniversityColumbusOHUSA
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Tokala R, Sana S, Lakshmi UJ, Sankarana P, Sigalapalli DK, Gadewal N, Kode J, Shankaraiah N. Design and synthesis of thiadiazolo-carboxamide bridged β-carboline-indole hybrids: DNA intercalative topo-IIα inhibition with promising antiproliferative activity. Bioorg Chem 2020; 105:104357. [PMID: 33091673 PMCID: PMC7543778 DOI: 10.1016/j.bioorg.2020.104357] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Revised: 09/03/2020] [Accepted: 10/05/2020] [Indexed: 02/05/2023]
Abstract
The conjoining of salient pharmacophoric properties directing the development of prominent cytotoxic agents was executed by constructing thiadiazolo-carboxamide bridged β-carboline-indole hybrids. On the evaluation of in vitro cytotoxic potential, 12c exhibited prodigious cytotoxicity among the synthesized new molecules 12a-k, with an IC50 < 5 μM in all the tested cancer cell lines (A549, MDA-MB-231, BT-474, HCT-116, THP-1) and the best cytotoxic potential was expressed in lung cancer cell line (A549) with an IC50 value of 2.82 ± 0.10 μM. Besides, another compound 12a also displayed impressive cytotoxicity against A549 cell line (IC50: 3.00 ± 1.40 μM). Further target-based assay of these two compounds 12c and 12a revealed their potential as DNA intercalative topoisomerase-IIα inhibitors. Additionally, the antiproliferative activity of compound 12c was measured in A549 cells by traditional apoptosis assays revealing the nuclear, morphological alterations, and depolarization of membrane potential in mitochondria and externalization of phosphatidylserine in a concentration-dependent manner. Cell cycle analysis unveiled the G0/G1 phase inhibition and wound healing assay inferred the inhibition of in vitro cell migration by compound 12c in lung cancer cells. Remarkably, the safety profile of compound 12c was disclosed by screening against normal human lung epithelial cell line (BEAS-2B: IC50: 71.2 ± 7.95 μM) with a selectivity index range of 14.9-25.26. Moreover, Molecular modeling studies affirm the intercalative binding of compound 12c and 12a in the active pocket of topo-IIα. Furthermore, in silico prediction of physico-chemical parameters divulged the propitious drug-like properties of the synthesized derivatives.
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Affiliation(s)
- Ramya Tokala
- Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research (NIPER), Hyderabad 500 037, India
| | - Sravani Sana
- Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research (NIPER), Hyderabad 500 037, India
| | - Uppu Jaya Lakshmi
- Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research (NIPER), Hyderabad 500 037, India
| | - Prasanthi Sankarana
- Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research (NIPER), Hyderabad 500 037, India
| | - Dilep Kumar Sigalapalli
- Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research (NIPER), Hyderabad 500 037, India
| | - Nikhil Gadewal
- Bioinformatics Centre, Advanced Centre for Treatment, Research & Education in Cancer, Tata Memorial Centre, Kharghar, Navi Mumbai 410210, India
| | - Jyoti Kode
- Tumor Immunology & Immunotherapy Group, Advanced Centre for Treatment, Research & Education in Cancer, Tata Memorial Centre, Kharghar, Navi Mumbai 410210, India; Homi-Bhabha National Institute (HBNI), Training School Complex, Anushakti Nagar, Mumbai 400094, India
| | - Nagula Shankaraiah
- Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research (NIPER), Hyderabad 500 037, India.
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Guo P. High resolution structure of hexameric herpesvirus DNA-packaging motor elucidates revolving mechanism and ends 20-year fervent debate. Protein Cell 2020; 11:311-315. [PMID: 32314326 PMCID: PMC7196596 DOI: 10.1007/s13238-020-00714-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Affiliation(s)
- Peixuan Guo
- College of Pharmacy, College of Medicine, Dorothy M. Davis Heart and Lung Research Institute, and Comprehensive Cancer Center, The Ohio State University, Columbus, OH, 43210, USA.
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Translation of the long-term fundamental studies on viral DNA packaging motors into nanotechnology and nanomedicine. SCIENCE CHINA-LIFE SCIENCES 2020; 63:1103-1129. [DOI: 10.1007/s11427-020-1752-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Accepted: 06/04/2020] [Indexed: 02/07/2023]
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Thaljeh LF, Rothschild JA, Naderi M, Coghill LM, Brown JM, Brylinski M. Hinge Region in DNA Packaging Terminase pUL15 of Herpes Simplex Virus: A Potential Allosteric Target for Antiviral Drugs. Biomolecules 2019; 9:biom9100603. [PMID: 31614784 PMCID: PMC6843332 DOI: 10.3390/biom9100603] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Revised: 09/30/2019] [Accepted: 10/08/2019] [Indexed: 12/23/2022] Open
Abstract
Approximately 80% of adults are infected with a member of the herpesviridae family. Herpesviruses establish life-long latent infections within neurons, which may reactivate into lytic infections due to stress or immune suppression. There are nine human herpesviruses (HHV) posing health concerns from benign conditions to life threatening encephalitis, including cancers associated with viral infections. The current treatment options for most HHV conditions mainly include several nucleoside and nucleotide analogs targeting viral DNA polymerase. Although these drugs help manage infections, their common mechanism of action may lead to the development of drug resistance, which is particularly devastating in immunocompromised patients. Therefore, new classes of drugs directed against novel targets in HHVs are necessary to alleviate this issue. We analyzed the conservation rates of all proteins in herpes simplex virus 1 (HHV-1), a representative of the HHV family and one of the most common viruses infecting the human population. Furthermore, we generated a full-length structure model of the most conserved HHV-1 protein, the DNA packaging terminase pUL15. A series of computational analyses were performed on the model to identify ATP and DNA binding sites and characterize the dynamics of the protein. Our study indicates that proteins involved in HHV-1 DNA packaging and cleavage are amongst the most conserved gene products of HHVs. Since the packaging protein pUL15 is the most conserved among all HHV-1 gene products, the virus will have a lower chance of developing resistance to small molecules targeting pUL15. A subsequent analysis of the structure of pUL15 revealed distinct ATP and DNA binding domains and the elastic network model identifies a functionally important hinge region between the two domains of pUL15. The atomic information on the active and allosteric sites in the ATP- and DNA-bound model of pUL15 presented in this study can inform the structure-based drug discovery of a new class of drugs to treat a wide range of HHVs.
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Affiliation(s)
- Lana F Thaljeh
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA.
| | - J Ainsley Rothschild
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA.
| | - Misagh Naderi
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA.
| | - Lyndon M Coghill
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA.
- Center for Computation & Technology, Louisiana State University, Baton Rouge, LA 70803, USA.
| | - Jeremy M Brown
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA.
| | - Michal Brylinski
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA.
- Center for Computation & Technology, Louisiana State University, Baton Rouge, LA 70803, USA.
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Guo P, Driver D, Zhao Z, Zheng Z, Chan C, Cheng X. Controlling the Revolving and Rotating Motion Direction of Asymmetric Hexameric Nanomotor by Arginine Finger and Channel Chirality. ACS NANO 2019; 13:6207-6223. [PMID: 31067030 PMCID: PMC6595433 DOI: 10.1021/acsnano.8b08849] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Nanomotors in nanotechnology are as important as engines in daily life. Many ATPases are nanoscale biomotors classified into three categories based on the motion mechanisms in transporting substrates: linear, rotating, and the recently discovered revolving motion. Most biomotors adopt a multisubunit ring-shaped structure that hydrolyzes ATP to generate force. How these biomotors control the motion direction and regulate the sequential action of their multiple subunits is intriguing. Many ATPases are hexameric with each monomer containing a conserved arginine finger. This review focuses on recent findings on how the arginine finger controls motion direction and coordinates adjacent subunit interactions in both revolving and rotating biomotors. Mechanisms of intersubunit interactions and sequential movements of individual subunits are evidenced by the asymmetrical appearance of one dimer and four monomers in high-resolution structural complexes. The arginine finger is situated at the interface of two subunits and extends into the ATP binding pocket of the downstream subunit. An arginine finger mutation results in deficiency in ATP binding/hydrolysis, substrate binding, and transport, highlighting the importance of the arginine finger in regulating energy transduction and motor function. Additionally, the roles of channel chirality and channel size are discussed as related to controlling one-way trafficking and differentiating the revolving and rotating mechanisms. Finally, the review concludes by discussing the conformational changes and entropy conversion triggered by ATP binding/hydrolysis, offering a view different from the traditional concept of ATP-mediated mechanochemical energy coupling. The elucidation of the motion mechanism and direction control in ATPases could facilitate nanomotor fabrication in nanotechnology.
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Affiliation(s)
- Peixuan Guo
- Center
for RNA Nanobiotechnology and Nanomedicine, College of Pharmacy
and College of Medicine, Dorothy M. Davis Heart and Lung Research
Institute, Comprehensive Cancer Center and College of Pharmacy, Biophysics
Graduate Program, Translational Data Analytics Institute, The Ohio State University, Columbus, Ohio 43210, United
States
- E-mail:
| | - Dana Driver
- Center
for RNA Nanobiotechnology and Nanomedicine, College of Pharmacy
and College of Medicine, Dorothy M. Davis Heart and Lung Research
Institute, Comprehensive Cancer Center and College of Pharmacy, Biophysics
Graduate Program, Translational Data Analytics Institute, The Ohio State University, Columbus, Ohio 43210, United
States
| | - Zhengyi Zhao
- Center
for RNA Nanobiotechnology and Nanomedicine, College of Pharmacy
and College of Medicine, Dorothy M. Davis Heart and Lung Research
Institute, Comprehensive Cancer Center and College of Pharmacy, Biophysics
Graduate Program, Translational Data Analytics Institute, The Ohio State University, Columbus, Ohio 43210, United
States
| | - Zhen Zheng
- Center
for RNA Nanobiotechnology and Nanomedicine, College of Pharmacy
and College of Medicine, Dorothy M. Davis Heart and Lung Research
Institute, Comprehensive Cancer Center and College of Pharmacy, Biophysics
Graduate Program, Translational Data Analytics Institute, The Ohio State University, Columbus, Ohio 43210, United
States
| | - Chun Chan
- Center
for RNA Nanobiotechnology and Nanomedicine, College of Pharmacy
and College of Medicine, Dorothy M. Davis Heart and Lung Research
Institute, Comprehensive Cancer Center and College of Pharmacy, Biophysics
Graduate Program, Translational Data Analytics Institute, The Ohio State University, Columbus, Ohio 43210, United
States
| | - Xiaolin Cheng
- Center
for RNA Nanobiotechnology and Nanomedicine, College of Pharmacy
and College of Medicine, Dorothy M. Davis Heart and Lung Research
Institute, Comprehensive Cancer Center and College of Pharmacy, Biophysics
Graduate Program, Translational Data Analytics Institute, The Ohio State University, Columbus, Ohio 43210, United
States
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Neuber S, Wagner K, Messerle M, Borst EM. The C-terminal part of the human cytomegalovirus terminase subunit pUL51 is central for terminase complex assembly. J Gen Virol 2018; 99:119-134. [DOI: 10.1099/jgv.0.000984] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Affiliation(s)
- Sebastian Neuber
- Institute of Virology, Hannover Medical School, Hannover, Germany
| | - Karen Wagner
- Institute of Virology, Hannover Medical School, Hannover, Germany
| | - Martin Messerle
- Institute of Virology, Hannover Medical School, Hannover, Germany
| | - Eva Maria Borst
- Institute of Virology, Hannover Medical School, Hannover, Germany
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Mutual Interplay between the Human Cytomegalovirus Terminase Subunits pUL51, pUL56, and pUL89 Promotes Terminase Complex Formation. J Virol 2017; 91:JVI.02384-16. [PMID: 28356534 DOI: 10.1128/jvi.02384-16] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2016] [Accepted: 03/17/2017] [Indexed: 01/05/2023] Open
Abstract
Human cytomegalovirus (HCMV) genome encapsidation requires several essential viral proteins, among them pUL56, pUL89, and the recently described pUL51, which constitute the viral terminase. To gain insight into terminase complex assembly, we investigated interactions between the individual subunits. For analysis in the viral context, HCMV bacterial artificial chromosomes carrying deletions in the open reading frames encoding the terminase proteins were used. These experiments were complemented by transient-transfection assays with plasmids expressing the terminase components. We found that if one terminase protein was missing, the levels of the other terminase proteins were markedly diminished, which could be overcome by proteasome inhibition or providing the missing subunit in trans These data imply that sequestration of the individual subunits within the terminase complex protects them from proteasomal turnover. The finding that efficient interactions among the terminase proteins occurred only when all three were present together is reminiscent of a folding-upon-binding principle leading to cooperative stability. Furthermore, whereas pUL56 was translocated into the nucleus on its own, correct nuclear localization of pUL51 and pUL89 again required all three terminase constituents. Altogether, these features point to a model of the HCMV terminase as a multiprotein complex in which the three players regulate each other concerning stability, subcellular localization, and assembly into the functional tripartite holoenzyme.IMPORTANCE HCMV is a major risk factor in immunocompromised individuals, and congenital CMV infection is the leading viral cause for long-term sequelae, including deafness and mental retardation. The current treatment of CMV disease is based on drugs sharing the same mechanism, namely, inhibiting viral DNA replication, and often results in adverse side effects and the appearance of resistant virus strains. Recently, the HCMV terminase has emerged as an auspicious target for novel antiviral drugs. A new drug candidate inhibiting the HCMV terminase, Letermovir, displayed excellent potency in clinical trials; however, its precise mode of action is not understood yet. Here, we describe the mutual dependence of the HCMV terminase constituents for their assembly into a functional terminase complex. Besides providing new basic insights into terminase formation, these results will be valuable when studying the mechanism of action for drugs targeting the HCMV terminase and developing additional substances interfering with viral genome encapsidation.
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An Arginine Finger Regulates the Sequential Action of Asymmetrical Hexameric ATPase in the Double-Stranded DNA Translocation Motor. Mol Cell Biol 2016; 36:2514-23. [PMID: 27457616 PMCID: PMC5021374 DOI: 10.1128/mcb.00142-16] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2016] [Accepted: 06/30/2016] [Indexed: 11/30/2022] Open
Abstract
Biological motors are ubiquitous in living systems. Currently, how the motor components coordinate the unidirectional motion is elusive in most cases. Here, we report that the sequential action of the ATPase ring in the DNA packaging motor of bacteriophage ϕ29 is regulated by an arginine finger that extends from one ATPase subunit to the adjacent unit to promote noncovalent dimer formation. Mutation of the arginine finger resulted in the interruption of ATPase oligomerization, ATP binding/hydrolysis, and DNA translocation. Dimer formation reappeared when arginine mutants were mixed with other ATPase subunits that can offer the arginine to promote their interaction. Ultracentrifugation and virion assembly assays indicated that the ATPase was presenting as monomers and dimer mixtures. The isolated dimer alone was inactive in DNA translocation, but the addition of monomer could restore the activity, suggesting that the hexameric ATPase ring contained both dimer and monomers. Moreover, ATP binding or hydrolysis resulted in conformation and entropy changes of the ATPase with high or low DNA affinity. Taking these observations together, we concluded that the arginine finger regulates sequential action of the motor ATPase subunit by promoting the formation of the dimer inside the hexamer. The finding of asymmetrical hexameric organization is supported by structural evidence of many other ATPase systems showing the presence of one noncovalent dimer and four monomer subunits. All of these provide clues for why the asymmetrical hexameric ATPase gp16 of ϕ29 was previously reported as a pentameric configuration by cryo-electron microscopy (cryo-EM) since the contact by the arginine finger renders two adjacent ATPase subunits closer than other subunits. Thus, the asymmetrical hexamer would appear as a pentamer by cryo-EM, a technology that acquires the average of many images.
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