1
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Varming AK, Huang Z, Hamad GM, Rasmussen KK, Ingmer H, Kilstrup M, Lo Leggio L. CI:Mor interactions in the lysogeny switches of Lactococcus lactis TP901-1 and Staphylococcus aureus φ13 bacteriophages. MICROBIOME RESEARCH REPORTS 2024; 3:15. [PMID: 38841409 PMCID: PMC11149083 DOI: 10.20517/mrr.2023.50] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Revised: 12/29/2023] [Accepted: 01/09/2024] [Indexed: 06/07/2024]
Abstract
Aim: To structurally characterize in detail the interactions between the phage repressor (CI) and the antirepressor (Mor) in the lysis-lysogeny switches of two Gram-positive bacteriophages, the lactococcal TP901-1 and staphylococcal φ13. Methods: We use crystallographic structure determination, computational structural modeling, and analysis, as well as biochemical methods, to elucidate similarities and differences in the CI:Mor interactions for the two genetic switches. Results: By comparing a newly determined and other available crystal structures for the N-terminal domain of CI (CI-NTD), we show that the CI interface involved in Mor binding undergoes structural changes upon binding in TP901-1. Most importantly, we show experimentally for the first time the direct interaction between CI and Mor for φ13, and model computationally the interaction interface. The computational modeling supports similar side chain rearrangements in TP901-1 and φ13. Conclusion: This study ascertains experimentally that, like in the TP901-1 lysogeny switch, staphylococcal φ13 CI and Mor interact with each other. The structural basis of the interaction of φ13 CI and Mor was computationally modeled and is similar to the interaction demonstrated experimentally between TP901-1 CI-NTD and Mor, likely involving similar rearrangement of residue side chains during the formation of the complex. The study identifies one CI residue, Glu69, which unusually interacts primarily through its aliphatic chain with an aromatic residue on Mor after changing its conformation compared to the un-complexed structure. This and other residues at the interface are suggested for investigation in future studies.
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Affiliation(s)
- Anders K. Varming
- Department of Chemistry, University of Copenhagen, Copenhagen DK-2100, Denmark
| | - Zhiyu Huang
- Department of Chemistry, University of Copenhagen, Copenhagen DK-2100, Denmark
| | - Ghofran M. Hamad
- Department of Chemistry, University of Copenhagen, Copenhagen DK-2100, Denmark
| | - Kim K. Rasmussen
- Department of Chemistry, University of Copenhagen, Copenhagen DK-2100, Denmark
| | - Hanne Ingmer
- Department of Veterinary and Animal Sciences, University of Copenhagen, Frederiksberg DK-1870, Denmark
| | - Mogens Kilstrup
- Department of Biotechnology and Biomedicine, Technical University of Denmark, Kongens Lyngby DK-2800, Denmark
| | - Leila Lo Leggio
- Department of Chemistry, University of Copenhagen, Copenhagen DK-2100, Denmark
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2
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Tucker MR, Piana S, Tan D, LeVine MV, Shaw DE. Development of Force Field Parameters for the Simulation of Single- and Double-Stranded DNA Molecules and DNA-Protein Complexes. J Phys Chem B 2022; 126:4442-4457. [PMID: 35694853 PMCID: PMC9234960 DOI: 10.1021/acs.jpcb.1c10971] [Citation(s) in RCA: 25] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
![]()
Although molecular
dynamics (MD) simulations have been used extensively
to study the structural dynamics of proteins, the role of MD simulation
in studies of nucleic acid based systems has been more limited. One
contributing factor to this disparity is the historically lower level
of accuracy of the physical models used in such simulations to describe
interactions involving nucleic acids. By modifying nonbonded and torsion
parameters of a force field from the Amber family of models, we recently
developed force field parameters for RNA that achieve a level of accuracy
comparable to that of state-of-the-art protein force fields. Here
we report force field parameters for DNA, which we developed by transferring
nonbonded parameters from our recently reported RNA force field and
making subsequent adjustments to torsion parameters. We have also
modified the backbone charges in both the RNA and DNA parameter sets
to make the treatment of electrostatics compatible with our recently
developed variant of the Amber protein and ion force field. We name
the force field resulting from the union of these three parameter
sets (the new DNA parameters, the revised RNA parameters, and the
existing protein and ion parameters) DES-Amber. Extensive
testing of DES-Amber indicates that it can describe the thermal stability
and conformational flexibility of single- and double-stranded DNA
systems with a level of accuracy comparable to or, especially for
disordered systems, exceeding that of state-of-the-art nucleic acid
force fields. Finally, we show that, in certain favorable cases, DES-Amber
can be used for long-timescale simulations of protein–nucleic
acid complexes.
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Affiliation(s)
| | - Stefano Piana
- D. E. Shaw Research, New York, New York 10036, United States
| | - Dazhi Tan
- D. E. Shaw Research, New York, New York 10036, United States
| | | | - David E Shaw
- D. E. Shaw Research, New York, New York 10036, United States.,Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032, United States
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3
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Varming AK, Rasmussen KK, Zong Z, Thulstrup PW, Kilstrup M, Lo Leggio L. Flexible linker modulates the binding affinity of the TP901-1 CI phage repressor to DNA. FEBS J 2021; 289:1135-1148. [PMID: 34665941 DOI: 10.1111/febs.16238] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 09/16/2021] [Accepted: 10/18/2021] [Indexed: 11/30/2022]
Abstract
Temperate bacteriophages can switch between two life cycles following infection of a host bacterium: the lytic or lysogenic life cycle. The choice between these is controlled by a bistable genetic switch. We investigated the genetic switch of the lactococcal temperate bacteriophage, TP901-1, which is controlled by two regulatory proteins, the Clear 1 (CI) repressor and modulator of repression (MOR) antirepressor. CI consists of a DNA-binding N-terminal domain and a C-terminal domain responsible for oligomerization, connected by a flexible interdomain linker. Full-length CI is hexameric, whereas the truncated version CI with 58 C-terminal residues truncated (CIΔ58), missing the second C-terminal subdomain, is dimeric, but binds with the same affinity as full-length CI to the OL operator site, responsible for lytic genes transcription repression. Three variants of CIΔ58 with shorter, longer, and PP substituted linkers were produced and confirmed by circular dichroism spectroscopy and nanodifferential scanning fluorimetry to be well folded. With small-angle X-ray scattering, we delineated the conformational space sampled by the variants and wild-type in solution and found that shortening and lengthening the linker decrease and increase this, respectively, as also substantiated by molecular dynamics and as intended. Isoelectric focusing electrophoresis confirmed that all variants are able to bind to the MOR antirepressor. However, using electrophoretic mobility shift assays, we showed that shortening and lengthening the linker lead to a 94 and 17 times decrease in affinity to OL , respectively. Thus, an appropriate linker length appears to be crucial for appropriate DNA-binding and subsequent TP901-1 genetic switch function.
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Affiliation(s)
| | | | - Zhiyou Zong
- Department of Chemistry, University of Copenhagen, Copenhagen, Denmark
| | | | - Mogens Kilstrup
- Department of Biotechnology and Biomedicine, Technical University of Denmark, Lyngby, Denmark
| | - Leila Lo Leggio
- Department of Chemistry, University of Copenhagen, Copenhagen, Denmark
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4
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Revealing the mechanism of repressor inactivation during switching of a temperate bacteriophage. Proc Natl Acad Sci U S A 2020; 117:20576-20585. [PMID: 32788352 DOI: 10.1073/pnas.2005218117] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Temperate bacteriophages can enter one of two life cycles following infection of a sensitive host: the lysogenic or the lytic life cycle. The choice between the two alternative life cycles is dependent upon a tight regulation of promoters and their cognate regulatory proteins within the phage genome. We investigated the genetic switch of TP901-1, a bacteriophage of Lactococcus lactis, controlled by the CI repressor and the modulator of repression (MOR) antirepressor and their interactions with DNA. We determined the solution structure of MOR, and we solved the crystal structure of MOR in complex with the N-terminal domain of CI, revealing the structural basis of MOR inhibition of CI binding to the DNA operator sites. 15N NMR Carr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion and rotating frame R 1ρ measurements demonstrate that MOR displays molecular recognition dynamics on two different time scales involving a repacking of aromatic residues at the interface with CI. Mutations in the CI:MOR binding interface impair complex formation in vitro, and when introduced in vivo, the bacteriophage switch is unable to choose the lytic life cycle showing that the CI:MOR complex is essential for proper functioning of the genetic switch. On the basis of sequence alignments, we show that the structural features of the MOR:CI complex are likely conserved among a larger family of bacteriophages from human pathogens implicated in transfer of antibiotic resistance.
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5
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Pedersen M, Neergaard JT, Cassias J, Rasmussen KK, Lo Leggio L, Sneppen K, Hammer K, Kilstrup M. Repression of the lysogenic P R promoter in bacteriophage TP901-1 through binding of a CI-MOR complex to a composite O M-O R operator. Sci Rep 2020; 10:8659. [PMID: 32457340 PMCID: PMC7250872 DOI: 10.1038/s41598-020-65493-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Accepted: 05/04/2020] [Indexed: 11/09/2022] Open
Abstract
A functional genetic switch from the lactococcal bacteriophage TP901-1, deciding which of two divergently transcribing promoters becomes most active and allows this bi-stable decision to be inherited in future generations requires a DNA region of less than 1 kb. The fragment encodes two repressors, CI and MOR, transcribed from the PR and PL promoters respectively. CI can repress the transcription of the mor gene at three operator sites (OR, OL, and OD), leading to the immune state. Repression of the cI gene, leading to the lytic (anti-immune) state, requires interaction between CI and MOR by an unknown mechanism, but involving a CI:MOR complex. A consensus for putative MOR binding sites (OM sites), and a common topology of three OM sites adjacent to the OR motif was here identified in diverse phage switches that encode CI and MOR homologs, in a search for DNA sequences similar to the TP901-1 switch. The OR site and all putative OM sites are important for establishment of the anti-immune repression of PR, and a putative DNA binding motif in MOR is needed for establishment of the anti-immune state. Direct evidence for binding between CI and MOR is here shown by pull-down experiments, chemical crosslinking, and size exclusion chromatography. The results are consistent with two possible models for establishment of the anti-immune repression of cI expression at the PR promoter.
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Affiliation(s)
- Margit Pedersen
- University of Copenhagen, Department of Biology, Copenhagen, DK2200, Denmark
| | - Jesper Tvenge Neergaard
- Technical University of Denmark, Department of Biotechnology and Biomedicine, Lyngby, DK2800, Denmark
| | - Johan Cassias
- Technical University of Denmark, Department of Biotechnology and Biomedicine, Lyngby, DK2800, Denmark
| | | | - Leila Lo Leggio
- University of Copenhagen, Department of Chemistry, Copenhagen, DK2200, Denmark
| | - Kim Sneppen
- University of Copenhagen, Center for Models of Life, Copenhagen, DK2200, Denmark
| | - Karin Hammer
- Technical University of Denmark, Department of Biotechnology and Biomedicine, Lyngby, DK2800, Denmark
| | - Mogens Kilstrup
- Technical University of Denmark, Department of Biotechnology and Biomedicine, Lyngby, DK2800, Denmark.
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6
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Biswas A, Ghosh S, Sinha D, Dutta A, Seal S, Bagchi A, Sau S. Dimerization ability, denaturation mechanism, and the stability of a staphylococcal phage repressor and its two domains. Int J Biol Macromol 2019; 124:903-914. [DOI: 10.1016/j.ijbiomac.2018.11.263] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Revised: 11/27/2018] [Accepted: 11/27/2018] [Indexed: 11/29/2022]
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7
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Li S, Hu R, Yao H, Long D, Luo F, Zhou X, Zhang X, Liu M, Zhu J, Yang Y. Characterization of the interaction interface and conformational dynamics of human TGIF1 homeodomain upon the binding of consensus DNA. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2018; 1866:1021-1028. [PMID: 30048701 DOI: 10.1016/j.bbapap.2018.07.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2018] [Revised: 05/28/2018] [Accepted: 07/17/2018] [Indexed: 01/17/2023]
Abstract
The TG interacting factor-1 homeodomain (TGIF1-HD) binds with the consensus DNA motif 5'-TGTCA-3' in gene promoters through its three-amino acid loop extension (TALE) type homeodomain, and then recruits co-regulators to regulate gene expression. Although the solution NMR structure of human TGIF1-HD has been reported previously, little is known about its DNA binding mechanism. NMR titrations have been extensively used to study mechanisms of ligand binding to target proteins; however, an intermediate exchange occurred predominantly between TGIF1-HD in the free and bound states when titrated with the consensus DNA, which resulted in poor-quality NMR spectra and precluded further exploration of its interaction interface and conformational dynamics. Here, the helix α3 of TGIF1-HD was speculated as the specific DNA binding interface by hydrogen-deuterium exchange mass spectrometry (HDX-MS) experiments, and subsequently confirmed by chemical exchange saturation transfer (CEST) spectroscopy. In addition, simultaneous conformational changes in other regions, including α1 and α2, were induced by DNA binding, explaining the observation of chemical shift perturbations from extensive residues besides those located in α3. Further, low-populated DNA-bound TGIF1-HD undergoing a slow exchange at a rate of 130.2 ± 3.6 s-1 was derived from the analysis of the CEST data, and two residues, R220 and R221, located in the middle of α3 were identified to be crucial for DNA binding. Our study provides structural and dynamic insights into the mechanisms of TGIF1-HD recognition of extensive promoter DNA.
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Affiliation(s)
- Shuangli Li
- State Key Laboratory of Magnetic Resonance and Atomic Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Chinese Academy of sciences, Wuhan 430071, China; Graduate University of Chinese Academy of Sciences, Beijing 100049, China
| | - Rui Hu
- State Key Laboratory of Magnetic Resonance and Atomic Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Chinese Academy of sciences, Wuhan 430071, China
| | - Haijie Yao
- School of Life Sciences, University of Science and Technology of China, Hefei 230027, China
| | - Dong Long
- School of Life Sciences, University of Science and Technology of China, Hefei 230027, China; Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230027, China
| | - Fan Luo
- State Key Laboratory of Magnetic Resonance and Atomic Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Chinese Academy of sciences, Wuhan 430071, China
| | - Xin Zhou
- State Key Laboratory of Magnetic Resonance and Atomic Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Chinese Academy of sciences, Wuhan 430071, China
| | - Xu Zhang
- State Key Laboratory of Magnetic Resonance and Atomic Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Chinese Academy of sciences, Wuhan 430071, China
| | - Maili Liu
- State Key Laboratory of Magnetic Resonance and Atomic Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Chinese Academy of sciences, Wuhan 430071, China
| | - Jiang Zhu
- State Key Laboratory of Magnetic Resonance and Atomic Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Chinese Academy of sciences, Wuhan 430071, China.
| | - Yunhuang Yang
- State Key Laboratory of Magnetic Resonance and Atomic Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Chinese Academy of sciences, Wuhan 430071, China.
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8
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Alanine substitution mutations in the DNA binding region of a global staphylococcal virulence regulator affect its structure, function, and stability. Int J Biol Macromol 2018; 113:1221-1232. [DOI: 10.1016/j.ijbiomac.2018.03.045] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Revised: 03/02/2018] [Accepted: 03/11/2018] [Indexed: 12/11/2022]
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9
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Rasmussen KK, Varming AK, Schmidt SN, Frandsen KEH, Thulstrup PW, Jensen MR, Lo Leggio L. Structural basis of the bacteriophage TP901-1 CI repressor dimerization and interaction with DNA. FEBS Lett 2018; 592:1738-1750. [PMID: 29683476 DOI: 10.1002/1873-3468.13060] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Revised: 04/12/2018] [Accepted: 04/12/2018] [Indexed: 12/31/2022]
Abstract
Temperate bacteriophages are known for their bistability, which in TP901-1 is controlled by two proteins, CI and MOR. Clear 1 repressor (CI) is hexameric and binds three palindromic operator sites via an N-terminal helix-turn-helix domain (NTD). A dimeric form, such as the truncated CI∆58 investigated here, is necessary for high-affinity binding to DNA. The crystal structure of the dimerization region (CTD1 ) is determined here, showing that it forms a pair of helical hooks. This newly determined structure is used together with the known crystal structure of the CI-NTD and small angle X-ray scattering data, to determine the solution structure of CI∆58 in complex with a palindromic operator site, showing that the two NTDs bind on opposing sides of the DNA helix.
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10
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Rasmussen KK, Frandsen KEH, Boeri Erba E, Pedersen M, Varming AK, Hammer K, Kilstrup M, Thulstrup PW, Blackledge M, Jensen MR, Lo Leggio L. Structural and dynamics studies of a truncated variant of CI repressor from bacteriophage TP901-1. Sci Rep 2016; 6:29574. [PMID: 27403839 PMCID: PMC4941734 DOI: 10.1038/srep29574] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Accepted: 06/17/2016] [Indexed: 11/28/2022] Open
Abstract
The CI repressor from the temperate bacteriophage TP901-1 consists of two folded domains, an N-terminal helix-turn-helix DNA-binding domain (NTD) and a C-terminal oligomerization domain (CTD), which we here suggest to be further divided into CTD1 and CTD2. Full-length CI is a hexameric protein, whereas a truncated version, CI∆58, forms dimers. We identify the dimerization region of CI∆58 as CTD1 and determine its secondary structure to be helical both within the context of CI∆58 and in isolation. To our knowledge this is the first time that a helical dimerization domain has been found in a phage repressor. We also precisely determine the length of the flexible linker connecting the NTD to the CTD. Using electrophoretic mobility shift assays and native mass spectrometry, we show that CI∆58 interacts with the OL operator site as one dimer bound to both half-sites, and with much higher affinity than the isolated NTD domain thus demonstrating cooperativity between the two DNA binding domains. Finally, using small angle X-ray scattering data and state-of-the-art ensemble selection techniques, we delineate the conformational space sampled by CI∆58 in solution, and we discuss the possible role that the dynamics play in CI-repressor function.
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Affiliation(s)
- Kim Krighaar Rasmussen
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, Copenhagen, Denmark
| | - Kristian E. H. Frandsen
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, Copenhagen, Denmark
| | | | - Margit Pedersen
- Department of Biology, University of Copenhagen, Ole Maaløes vej 5, DK-2200 Copenhagen N, Denmark
| | - Anders K. Varming
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, Copenhagen, Denmark
| | - Karin Hammer
- Metabolic signalling and regulation, Department of Systems Biology, Technical University of Denmark, DK-2800 Lyngby, Denmark
| | - Mogens Kilstrup
- Metabolic signalling and regulation, Department of Systems Biology, Technical University of Denmark, DK-2800 Lyngby, Denmark
| | - Peter W. Thulstrup
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, Copenhagen, Denmark
| | - Martin Blackledge
- Univ. Grenoble Alpes, CNRS, CEA, Institut de Biologie Structurale, Grenoble, France
| | | | - Leila Lo Leggio
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, Copenhagen, Denmark
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11
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Abstract
We report a method for obtaining turbid plaques of the lactococcal bacteriophage TP901-1 and its derivative TP901-BC1034. We have further used the method to isolate clear plaque mutants of this phage. Analysis of 8 such mutants that were unable to lysogenize the host included whole genome resequencing. Four of the mutants had different mutations in structural genes with no relation to the genetic switch. However all 8 mutants had a mutation in the cI repressor gene region. Three of these were located in the promoter and Shine-Dalgarno sequences and five in the N-terminal part of the encoded CI protein involved in the DNA binding. The conclusion is that cI is the only gene involved in clear plaque formation i.e. the CI protein is the determining factor for the lysogenic pathway and its maintenance in the lactococcal phage TP901-1.
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12
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Biswas A, Mandal S, Sau S. The N-terminal domain of the repressor of Staphylococcus aureus phage Φ11 possesses an unusual dimerization ability and DNA binding affinity. PLoS One 2014; 9:e95012. [PMID: 24747758 PMCID: PMC3991615 DOI: 10.1371/journal.pone.0095012] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2013] [Accepted: 03/22/2014] [Indexed: 11/19/2022] Open
Abstract
Bacteriophage Φ11 uses Staphylococcus aureus as its host and, like lambdoid phages, harbors three homologous operators in between its two divergently oriented repressor genes. None of the repressors of Φ11, however, showed binding to all three operators, even at high concentrations. To understand why the DNA binding mechanism of Φ11 repressors does not match that of lambdoid phage repressors, we studied the N-terminal domain of the Φ11 lysogenic repressor, as it harbors a putative helix-turn-helix motif. Our data revealed that the secondary and tertiary structures of the N-terminal domain were different from those of the full-length repressor. Nonetheless, the N-terminal domain was able to dimerize and bind to the operators similar to the intact repressor. In addition, the operator base specificity, binding stoichiometry, and binding mechanism of this domain were nearly identical to those of the whole repressor. The binding affinities of the repressor and its N-terminal domain were reduced to a similar extent when the temperature was increased to 42°C. Both proteins also adequately dislodged a RNA polymerase from a Φ11 DNA fragment carrying two operators and a promoter. Unlike the intact repressor, the binding of the N-terminal domain to two adjacent operator sites was not cooperative in nature. Taken together, we suggest that the dimerization and DNA binding abilities of the N-terminal domain of the Φ11 repressor are distinct from those of the DNA binding domains of other phage repressors.
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Affiliation(s)
- Anindya Biswas
- Department of Biochemistry, Bose Institute, Kolkata, West Bengal, India
| | - Sukhendu Mandal
- Department of Biochemistry, Bose Institute, Kolkata, West Bengal, India
| | - Subrata Sau
- Department of Biochemistry, Bose Institute, Kolkata, West Bengal, India
- * E-mail:
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