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-Structure paper
Title | Structural asymmetry governs the assembly and GTPase activity of McrBC restriction complexes. |
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Journal, issue, pages | Nat Commun, Vol. 11, Issue 1, Page 5907, Year 2020 |
Publish date | Nov 20, 2020 |
Authors | Yiming Niu / Hiroshi Suzuki / Christopher J Hosford / Thomas Walz / Joshua S Chappie / |
PubMed Abstract | McrBC complexes are motor-driven nucleases functioning in bacterial self-defense by cleaving foreign DNA. The GTP-specific AAA + protein McrB powers translocation along DNA and its hydrolysis ...McrBC complexes are motor-driven nucleases functioning in bacterial self-defense by cleaving foreign DNA. The GTP-specific AAA + protein McrB powers translocation along DNA and its hydrolysis activity is stimulated by its partner nuclease McrC. Here, we report cryo-EM structures of Thermococcus gammatolerans McrB and McrBC, and E. coli McrBC. The McrB hexamers, containing the necessary catalytic machinery for basal GTP hydrolysis, are intrinsically asymmetric. This asymmetry directs McrC binding so that it engages a single active site, where it then uses an arginine/lysine-mediated hydrogen-bonding network to reposition the asparagine in the McrB signature motif for optimal catalytic function. While the two McrBC complexes use different DNA-binding domains, these contribute to the same general GTP-recognition mechanism employed by all G proteins. Asymmetry also induces distinct inter-subunit interactions around the ring, suggesting a coordinated and directional GTP-hydrolysis cycle. Our data provide insights into the conserved molecular mechanisms governing McrB family AAA + motors. |
External links | Nat Commun / PubMed:33219217 / PubMed Central |
Methods | EM (single particle) / X-ray diffraction |
Resolution | 2.44 - 4.26 Å |
Structure data | EMDB-20865, PDB-6ut4: EMDB-20866, PDB-6ut5: EMDB-20867, PDB-6ut6: EMDB-20868: Full map of the tetradecameric assembly of Thermococcus gammatolerans McrB AAA+ hexamers with bound McrC in C2 symmetry EMDB-20869: EMDB-20870: EMDB-20871: Combined map of the half-complex from tetradecameric assembly of Thermococcus gammatolerans McrB AAA+ hexamers with bound McrC PDB-6ut3: |
Chemicals | ChemComp-MG: ChemComp-GSP: ChemComp-HOH: ChemComp-GDP: |
Source |
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Keywords | DNA BINDING PROTEIN / AAA protein / GTPase / Methylation-dependent restriction / Endonuclease |