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Qian JW, Wang XY, Deng K, Li DF, Guo L. Crystal structure of the chromosome partition protein MukE homodimer. Biochem Biophys Res Commun 2021; 589:229-233. [PMID: 34929446 DOI: 10.1016/j.bbrc.2021.12.032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2021] [Revised: 12/08/2021] [Accepted: 12/12/2021] [Indexed: 11/15/2022]
Abstract
The SMC (structural maintenance of chromosomes) proteins are known to be involved in chromosome pairing or aggregation and play an important role in cell cycle and division. Different from SMC-ScpAB complex maintaining chromosome structure in most bacteria, the MukB-MukE-MukF complex is responsible for chromosome condensation in E. coli and some γ-proteobacter. Though different models were proposed to illustrate the mechanism of how the MukBEF complex worked, the assembly of the MukBEF complex is a key. The MukE dimer interacted with the middle region of one MukF molecule, and was clamped by the N- and C-terminal domain of the latter, and then was involved in the interaction with the head domain of MukB. To reveal the structural basis of MukE involved in the dynamic equilibrium of potential different MukBEF assemblies, we determined the MukE structure at 2.44 Å resolution. We found that the binding cavity for the α10, β4 and β5 of MukF (residues 296-327) in the MukE dimer has been occupied by the α9 and β7 strand of MukE. We proposed that the highly dynamic C-terminal region (173-225) was important for the MukE-F assembly and then involved in the MukBEF complex formation.
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Affiliation(s)
- Jia-Wei Qian
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China; College of Life and Health Sciences, Northeastern University, Shenyang, 110169, China
| | - Xiao-Yan Wang
- Department of Biochemistry and Molecular Biology, College of Basic Medicine, Hubei University of Medicine, Shiyan, 442000, China
| | - Kai Deng
- Reproductive Medicine Center, Renmin Hospital, Hubei University of Medicine, Shiyan, 442000, China
| | - De-Feng Li
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China; College of Life Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Lu Guo
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China; College of Life Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China.
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Bürmann F, Funke LFH, Chin JW, Löwe J. Cryo-EM structure of MukBEF reveals DNA loop entrapment at chromosomal unloading sites. Mol Cell 2021; 81:4891-4906.e8. [PMID: 34739874 PMCID: PMC8669397 DOI: 10.1016/j.molcel.2021.10.011] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 08/31/2021] [Accepted: 10/12/2021] [Indexed: 11/25/2022]
Abstract
The ring-like structural maintenance of chromosomes (SMC) complex MukBEF folds the genome of Escherichia coli and related bacteria into large loops, presumably by active DNA loop extrusion. MukBEF activity within the replication terminus macrodomain is suppressed by the sequence-specific unloader MatP. Here, we present the complete atomic structure of MukBEF in complex with MatP and DNA as determined by electron cryomicroscopy (cryo-EM). The complex binds two distinct DNA double helices corresponding to the arms of a plectonemic loop. MatP-bound DNA threads through the MukBEF ring, while the second DNA is clamped by the kleisin MukF, MukE, and the MukB ATPase heads. Combinatorial cysteine cross-linking confirms this topology of DNA loop entrapment in vivo. Our findings illuminate how a class of near-ubiquitous DNA organizers with important roles in genome maintenance interacts with the bacterial chromosome.
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Affiliation(s)
- Frank Bürmann
- MRC Laboratory of Molecular Biology, Structural Studies Division, Cambridge Biomedical Campus, Cambridge, UK.
| | - Louise F H Funke
- MRC Laboratory of Molecular Biology, Protein and Nucleic Acid Chemistry Division, Cambridge Biomedical Campus, Cambridge, UK
| | - Jason W Chin
- MRC Laboratory of Molecular Biology, Protein and Nucleic Acid Chemistry Division, Cambridge Biomedical Campus, Cambridge, UK
| | - Jan Löwe
- MRC Laboratory of Molecular Biology, Structural Studies Division, Cambridge Biomedical Campus, Cambridge, UK.
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Vondrova L, Kolesar P, Adamus M, Nociar M, Oliver AW, Palecek JJ. A role of the Nse4 kleisin and Nse1/Nse3 KITE subunits in the ATPase cycle of SMC5/6. Sci Rep 2020; 10:9694. [PMID: 32546830 PMCID: PMC7297730 DOI: 10.1038/s41598-020-66647-w] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Accepted: 05/20/2020] [Indexed: 12/03/2022] Open
Abstract
The SMC (Structural Maintenance of Chromosomes) complexes are composed of SMC dimers, kleisin and kleisin-interacting (HAWK or KITE) subunits. Mutual interactions of these subunits constitute the basal architecture of the SMC complexes. In addition, binding of ATP molecules to the SMC subunits and their hydrolysis drive dynamics of these complexes. Here, we developed new systems to follow the interactions between SMC5/6 subunits and the relative stability of the complex. First, we show that the N-terminal domain of the Nse4 kleisin molecule binds to the SMC6 neck and bridges it to the SMC5 head. Second, binding of the Nse1 and Nse3 KITE proteins to the Nse4 linker increased stability of the ATP-free SMC5/6 complex. In contrast, binding of ATP to SMC5/6 containing KITE subunits significantly decreased its stability. Elongation of the Nse4 linker partially suppressed instability of the ATP-bound complex, suggesting that the binding of the KITE proteins to the Nse4 linker constrains its limited size. Our data suggest that the KITE proteins may shape the Nse4 linker to fit the ATP-free complex optimally and to facilitate opening of the complex upon ATP binding. This mechanism suggests an important role of the KITE subunits in the dynamics of the SMC5/6 complexes.
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Affiliation(s)
- Lucie Vondrova
- National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Kamenice 5, 62500, Brno, Czech Republic
| | - Peter Kolesar
- National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Kamenice 5, 62500, Brno, Czech Republic
| | - Marek Adamus
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk University, Kamenice 5, 62500, Brno, Czech Republic
| | - Matej Nociar
- National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Kamenice 5, 62500, Brno, Czech Republic
| | - Antony W Oliver
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer, Brighton, BN1 9RQ, United Kingdom
| | - Jan J Palecek
- National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Kamenice 5, 62500, Brno, Czech Republic. .,Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk University, Kamenice 5, 62500, Brno, Czech Republic.
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4
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Abstract
Structural maintenance of chromosomes (SMC) complexes are key organizers of chromosome architecture in all kingdoms of life. Despite seemingly divergent functions, such as chromosome segregation, chromosome maintenance, sister chromatid cohesion, and mitotic chromosome compaction, it appears that these complexes function via highly conserved mechanisms and that they represent a novel class of DNA translocases.
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Affiliation(s)
- Stanislau Yatskevich
- Laboratory of Molecular Biology, Medical Research Council, Cambridge University, Cambridge CB2 0QH, United Kingdom
| | - James Rhodes
- Department of Biochemistry, Oxford University, Oxford OX1 3QU, United Kingdom;
| | - Kim Nasmyth
- Department of Biochemistry, Oxford University, Oxford OX1 3QU, United Kingdom;
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5
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Zawadzka K, Zawadzki P, Baker R, Rajasekar KV, Wagner F, Sherratt DJ, Arciszewska LK. MukB ATPases are regulated independently by the N- and C-terminal domains of MukF kleisin. eLife 2018; 7:31522. [PMID: 29323635 PMCID: PMC5812716 DOI: 10.7554/elife.31522] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Accepted: 01/10/2018] [Indexed: 12/21/2022] Open
Abstract
The Escherichia coli SMC complex, MukBEF, acts in chromosome segregation. MukBEF shares the distinctive architecture of other SMC complexes, with one prominent difference; unlike other kleisins, MukF forms dimers through its N-terminal domain. We show that a 4-helix bundle adjacent to the MukF dimerisation domain interacts functionally with the MukB coiled-coiled ‘neck’ adjacent to the ATPase head. We propose that this interaction leads to an asymmetric tripartite complex, as in other SMC complexes. Since MukF dimerisation is preserved during this interaction, MukF directs the formation of dimer of dimer MukBEF complexes, observed previously in vivo. The MukF N- and C-terminal domains stimulate MukB ATPase independently and additively. We demonstrate that impairment of the MukF interaction with MukB in vivo leads to ATP hydrolysis-dependent release of MukBEF complexes from chromosomes. Most DNA in a cell is arranged in structures called chromosomes. From bacteria to humans, chromosomes have to be compacted and highly organized to allow the cells to maintain and use their genetic information. In all organisms, large ring-shaped protein complexes play a crucial role in managing chromosomes. They transport and organize DNA thanks to reactions whose precise mechanism remains unknown. In bacteria, MukB and a type of kleisin called MukF are two examples of molecules involved in chromosome management. Two MukBs join at one end to form a hinge; at the other end, each MukB protein has a neck and a head. The two heads are linked by the kleisin to form a large protein ring, which can open to capture DNA. The MukB heads can trigger a biochemical reaction that creates the energy essential to trap and release DNA during DNA transport. Here, Zawadzka et al. study how the different components of the MukB-kleisin complex interact with each other to undergo the biochemical reactions that lead to DNA transport. The experiments show that the kleisin joins two MukB heads by attaching the base of one to the neck of the other, asymmetrically closing the ring. The separate interactions of different regions of the kleisin to the head and neck of MukB independently activate the two MukB heads, thereby controlling essential steps in the reactions with DNA. Two MukB-kleisin ring complexes are joined to each other because of a tight interaction between the two kleisin molecules. This leads Zawadzka et al. to suggest that DNA is sequentially grabbed and released from these two rings during DNA transport, similar to how a climbing rope is attached and released through carabiners. Cells cannot survive or be healthy without their chromosomes being accurately managed. It is still unclear how molecules such as MukBs and kleinsins drive this process. A better picture of their structure and interactions is an essential first step to understand these mechanisms.
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Affiliation(s)
- Katarzyna Zawadzka
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Pawel Zawadzki
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Rachel Baker
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | | | - Florence Wagner
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - David J Sherratt
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
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6
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Palecek JJ, Gruber S. Kite Proteins: a Superfamily of SMC/Kleisin Partners Conserved Across Bacteria, Archaea, and Eukaryotes. Structure 2015; 23:2183-2190. [DOI: 10.1016/j.str.2015.10.004] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Revised: 09/23/2015] [Accepted: 10/01/2015] [Indexed: 10/22/2022]
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Structural basis for microtubule recognition by the human kinetochore Ska complex. Nat Commun 2015; 5:2964. [PMID: 24413531 PMCID: PMC3923297 DOI: 10.1038/ncomms3964] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2013] [Accepted: 11/20/2013] [Indexed: 11/08/2022] Open
Abstract
The ability of kinetochores (KTs) to maintain stable attachments to dynamic microtubule structures ('straight' during microtubule polymerization and 'curved' during microtubule depolymerization) is an essential requirement for accurate chromosome segregation. Here we show that the kinetochore-associated Ska complex interacts with tubulin monomers via the carboxy-terminal winged-helix domain of Ska1, providing the structural basis for the ability to bind both straight and curved microtubule structures. This contrasts with the Ndc80 complex, which binds straight microtubules by recognizing the dimeric interface of tubulin. The Ska1 microtubule-binding domain interacts with tubulins using multiple contact sites that allow the Ska complex to bind microtubules in multiple modes. Disrupting either the flexibility or the tubulin contact sites of the Ska1 microtubule-binding domain perturbs normal mitotic progression, explaining the critical role of the Ska complex in maintaining a firm grip on dynamic microtubules.
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Rybenkov VV, Herrera V, Petrushenko ZM, Zhao H. MukBEF, a chromosomal organizer. J Mol Microbiol Biotechnol 2015; 24:371-83. [PMID: 25732339 DOI: 10.1159/000369099] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Global folding of bacterial chromosome requires the activity of condensins. These highly conserved proteins are involved in various aspects of higher-order chromatin dynamics in a diverse range of organisms. Two distinct superfamilies of condensins have been identified in bacteria. The SMC-ScpAB proteins bear significant homology to eukaryotic condensins and cohesins and are found in most of the presently sequenced bacteria. This review focuses on the MukBEF/MksBEF superfamily, which is broadly distributed across diverse bacteria and is characterized by low sequence conservation. The prototypical member of this superfamily, the Escherichia coli condensin MukBEF, continues to provide critical insights into the mechanism of the proteins. MukBEF acts as a complex molecular machine that assists in chromosome segregation and global organization. The review focuses on the mechanistic analysis of DNA organization by MukBEF with emphasis on its involvement in the formation of chromatin scaffold and plausible other roles in chromosome segregation.
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Affiliation(s)
- Valentin V Rybenkov
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Okla., USA
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Eng T, Guacci V, Koshland D. ROCC, a conserved region in cohesin's Mcd1 subunit, is essential for the proper regulation of the maintenance of cohesion and establishment of condensation. Mol Biol Cell 2014; 25:2351-64. [PMID: 24966169 PMCID: PMC4142609 DOI: 10.1091/mbc.e14-04-0929] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2014] [Revised: 06/16/2014] [Accepted: 06/18/2014] [Indexed: 12/25/2022] Open
Abstract
Cohesin helps orchestrate higher-order chromosome structure, thereby promoting sister chromatid cohesion, chromosome condensation, DNA repair, and transcriptional regulation. To elucidate how cohesin facilitates these diverse processes, we mutagenized Mcd1p, the kleisin regulatory subunit of budding yeast cohesin. In the linker region of Mcd1p, we identified a novel evolutionarily conserved 10-amino acid cluster, termed the regulation of cohesion and condensation (ROCC) box. We show that ROCC promotes cohesion maintenance by protecting a second activity of cohesin that is distinct from its stable binding to chromosomes. The existence of this second activity is incompatible with the simple embrace mechanism of cohesion. In addition, we show that the ROCC box is required for the establishment of condensation. We provide evidence that ROCC controls cohesion maintenance and condensation establishment through differential functional interactions with Pds5p and Wpl1p.
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Affiliation(s)
- Thomas Eng
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
| | - Vincent Guacci
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
| | - Doug Koshland
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
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10
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Nolivos S, Sherratt D. The bacterial chromosome: architecture and action of bacterial SMC and SMC-like complexes. FEMS Microbiol Rev 2013; 38:380-92. [PMID: 24118085 PMCID: PMC4255302 DOI: 10.1111/1574-6976.12045] [Citation(s) in RCA: 94] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Revised: 08/09/2013] [Accepted: 08/26/2013] [Indexed: 12/27/2022] Open
Abstract
Structural Maintenance of Chromosomes (SMC) protein complexes are found in all three domains of life. They are characterized by a distinctive and conserved architecture in which a globular ATPase ‘head’ domain is formed by the N- and C-terminal regions of the SMC protein coming together, with a c. 50-nm-long antiparallel coiled-coil separating the head from a dimerization ‘hinge’. Dimerization gives both V- and O-shaped SMC dimers. The distinctive architecture points to a conserved biochemical mechanism of action. However, the details of this mechanism are incomplete, and the precise ways in which this mechanism leads to the biological functions of these complexes in chromosome organization and processing remain unclear. In this review, we introduce the properties of bacterial SMC complexes, compare them with eukaryotic complexes and discuss how their likely biochemical action relates to their roles in chromosome organization and segregation.
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Affiliation(s)
- Sophie Nolivos
- Department of Biochemistry, University of Oxford, Oxford, UK
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11
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Kamada K, Miyata M, Hirano T. Molecular basis of SMC ATPase activation: role of internal structural changes of the regulatory subcomplex ScpAB. Structure 2013; 21:581-94. [PMID: 23541893 DOI: 10.1016/j.str.2013.02.016] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2013] [Revised: 02/14/2013] [Accepted: 02/17/2013] [Indexed: 11/18/2022]
Abstract
In many bacteria, a homodimer of structural-maintenance-of-chromosomes proteins associates with two regulatory subunits (known as ScpA and ScpB), assembling a protein complex that plays a crucial role in chromosome organization and segregation. It remains poorly understood, however, how this complex might work at the mechanistic level. Here, we report crystal structures of the ScpAB core complex that display a highly unusual structure in which the central segment of ScpA winds around an asymmetrically oriented ScpB dimer. The two C-terminal domains of the ScpB dimer primarily interact with different regions of ScpA with different affinities. Moreover, flexible interdomain regions of ScpB contribute to a dynamic folding process of the ScpAB subcomplex. Together with other genetic and biochemical assays, we provide evidence that internal structural changes of the ScpAB subcomplex are tightly coupled with activation of the structural-maintenance-of-chromosomes ATPase.
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Affiliation(s)
- Katsuhiko Kamada
- Chromosome Dynamics Laboratory, RIKEN Advanced Science Institute, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
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12
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She W, Mordukhova E, Zhao H, Petrushenko ZM, Rybenkov VV. Mutational analysis of MukE reveals its role in focal subcellular localization of MukBEF. Mol Microbiol 2012; 87:539-52. [PMID: 23171168 DOI: 10.1111/mmi.12112] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/19/2012] [Indexed: 11/26/2022]
Abstract
Bacterial condensin MukBEF is essential for global folding of the Escherichia coli chromosome. MukB, a SMC (structural maintenance of chromosome) protein, comprises the core of this complex and is responsible for its ATP-modulated DNA binding and reshaping activities. MukF serves as a kleisin that modulates MukB-DNA interactions and links MukBs into macromolecular assemblies. Little is known about the function of MukE. Using random mutagenesis, we generated six loss-of-function point mutations in MukE. The surface mutations clustered in two places. One of them was at or close to the interface with MukF while the other was away from the known interactions of the protein. All loss-of-function mutations affected focal localization of MukBEF in live cells. In vitro, however, only some of them interfered with the assembly of MukBEF into a complex or the ability of MukEF to disrupt MukB-DNA interactions. Moreover, some MukE mutants were able to join intracellular foci formed by endogenous MukBEF and most of the mutants were efficiently incorporated into MukBEF even in the presence of endogenous MukE. These data reveal that focal localization of MukBEF involves other activities besides DNA binding and that MukE plays a central role in them.
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Affiliation(s)
- Weifeng She
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, OK 73019, USA
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13
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Badrinarayanan A, Reyes-Lamothe R, Uphoff S, Leake MC, Sherratt DJ. In vivo architecture and action of bacterial structural maintenance of chromosome proteins. Science 2012; 338:528-31. [PMID: 23112333 PMCID: PMC3807729 DOI: 10.1126/science.1227126] [Citation(s) in RCA: 186] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
SMC (structural maintenance of chromosome) proteins act ubiquitously in chromosome processing. In Escherichia coli, the SMC complex MukBEF plays roles in chromosome segregation and organization. We used single-molecule millisecond multicolor fluorescence microscopy of live bacteria to reveal that a dimer of dimeric fluorescent MukBEF molecules acts as the minimal functional unit. On average, 8 to 10 of these complexes accumulated as "spots" in one to three discrete chromosome-associated regions of the cell, where they formed higher-order structures. Functional MukBEF within spots exchanged with freely diffusing complexes at a rate of one complex about every 50 seconds in reactions requiring adenosine triphosphate (ATP) hydrolysis. Thus, by functioning in pairs, MukBEF complexes may undergo multiple cycles of ATP hydrolysis without being released from DNA, analogous to the behavior of well-characterized molecular motors.
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14
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Teichmann M, Dumay-Odelot H, Fribourg S. Structural and functional aspects of winged-helix domains at the core of transcription initiation complexes. Transcription 2012; 3:2-7. [PMID: 22456313 DOI: 10.4161/trns.3.1.18917] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The winged helix (WH) domain is found in core components of transcription systems in eukaryotes and prokaryotes. It represents a sub-class of the helix-turn-helix motif. The WH domain participates in establishing protein-DNA and protein-protein-interactions. Here, we discuss possible explanations for the enrichment of this motif in transcription systems.
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Affiliation(s)
- Martin Teichmann
- Université de Bordeaux, Institut Européen de Chimie et Biologie, Pessac, France
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15
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Fuentes-Perez ME, Gwynn EJ, Dillingham MS, Moreno-Herrero F. Using DNA as a fiducial marker to study SMC complex interactions with the atomic force microscope. Biophys J 2012; 102:839-48. [PMID: 22385855 DOI: 10.1016/j.bpj.2012.01.022] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2011] [Revised: 01/10/2012] [Accepted: 01/17/2012] [Indexed: 01/21/2023] Open
Abstract
Atomic force microscopy can potentially provide information on protein volumes, shapes, and interactions but is susceptible to variable tip-induced artifacts. In this study, we present an atomic force microscopy approach that can measure volumes of nonglobular polypeptides such as structural maintenance of chromosomes (SMC) proteins, and use it to study the interactions that occur within and between SMC complexes. Together with the protein of interest, we coadsorb a DNA molecule and use it as a fiducial marker to account for tip-induced artifacts that affect both protein and DNA, allowing normalization of protein volumes from images taken on different days and with different tips. This approach significantly reduced the error associated with volume analysis, and allowed determination of the oligomeric states and architecture of the Bacillus subtilis SMC complex, formed by the SMC protein, and by the smaller ScpA and ScpB subunits. This work reveals that SMC and ScpB are dimers and that ScpA is a stable monomer. Moreover, whereas ScpA binds directly to SMC, ScpB only binds to SMC in the presence of ScpA. Notably, the presence of both ScpA and ScpB favored the formation of higher-order structures of SMC complexes, suggesting a role for these subunits in the organization of SMC oligomers.
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Affiliation(s)
- M E Fuentes-Perez
- Department of Macromolecular Structures, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas, Madrid, Spain
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