Abstract
Eukaryotic structural maintenance of chromosomes (SMC)-kleisin complexes form large, ring-shaped assemblies that promote accurate chromosome segregation. Their asymmetric structural core comprises SMC heterodimers that associate with both ends of a kleisin subunit. However, prokaryotic condensin Smc-ScpAB is composed of symmetric Smc homodimers associated with the kleisin ScpA in a postulated symmetrical manner. Here, we demonstrate that Smc molecules have two distinct binding sites for ScpA. The N terminus of ScpA binds the Smc coiled coil, whereas the C terminus binds the Smc ATPase domain. We show that in Bacillus subtilis cells, an Smc dimer is bridged by a single ScpAB to generate asymmetric tripartite rings analogous to eukaryotic SMC complexes. We define a molecular mechanism that ensures asymmetric assembly, and we conclude that the basic architecture of SMC-kleisin rings evolved before the emergence of eukaryotes.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Adenosine Triphosphatases / chemistry*
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Adenosine Triphosphatases / metabolism
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Bacterial Proteins / chemistry*
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Bacterial Proteins / genetics
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Bacterial Proteins / metabolism
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Binding Sites
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Cell Cycle Proteins / chemistry*
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Cell Cycle Proteins / genetics
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Cell Cycle Proteins / metabolism
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Cross-Linking Reagents
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Crystallography, X-Ray
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DNA-Binding Proteins / chemistry*
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DNA-Binding Proteins / metabolism
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Models, Molecular
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Multiprotein Complexes / chemistry*
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Multiprotein Complexes / metabolism
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Mutation
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Protein Conformation
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Protein Multimerization
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Protein Structure, Tertiary
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Streptococcus pneumoniae / chemistry
Substances
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Bacterial Proteins
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Cell Cycle Proteins
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Cross-Linking Reagents
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DNA-Binding Proteins
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Multiprotein Complexes
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SMC protein, Bacteria
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ScpA protein, Bacillus subtilis
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condensin complexes
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Adenosine Triphosphatases
Associated data
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PDB/3ZGX
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PDB/4I98
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PDB/4I99