Database of articles cited by EMDB/PDB/SASBDB data

Keywords
Structure methods	All X-ray diffraction NMR electron microscopy small angle scattering neutron diffraction fiber diffraction powder diffraction infrared spectroscopy EPR fluorescence transfer theoretical model Hybrid
Author
Journal
IF	>30 >20 >10 >5 all

Title	Structural and functional characterization of SPARTA system.
Journal, issue, pages	Biochem Biophys Res Commun, Vol. 825, Page 153972, Year 2026
Publish date	Aug 6, 2026
Authors	Hongze Zhao / Pingping Huang / Lijie Guo / Xinning Jiang / Zhaoxing Li / Bingjie Tao / Meiling Lu / Lianwen Qi / Lei Zhang / Yibei Xiao / Meirong Chen /
PubMed Abstract	Short prokaryotic Argonaute associated with TIR-APAZ (SPARTA) is a bacterial defense system that oligomerizes to activate the TIR domain, depleting NAD upon guide-mediated target DNA recognition. ...Short prokaryotic Argonaute associated with TIR-APAZ (SPARTA) is a bacterial defense system that oligomerizes to activate the TIR domain, depleting NAD upon guide-mediated target DNA recognition. Previous studies have shown a marked activity divergence between thermophilic Crenotalea thermophila SPARTA (CrtSPARTA) and Maribacter polysiphoniae SPARTA (MapSPARTA); however, the underlying mechanism remains unclear. Here, through biochemical and structural analysis, we found that compared with the relatively rigid CrtSPARTA, MapSPARTA exhibits much more flexibility in its TIR domain, which flips during the formation of active tetramers. Interestingly, we found that the activity of CrtSPARTA, but not MapSPARTA, could be significantly enhanced when we weakened the interaction between the MID and TIR domains by introducing mutations at the interface, suggesting that the MID-TIR interaction restricts the release of CrtTIR and thus the activation of CrtSPARTA. Following guide-target recognition, this flexibility-induced activation can be further promoted by higher temperatures within the physiological range or Ca, together suggesting that the restriction of TIR by the MID-TIR interaction may be a strategy to prevent auto-activation of thermophilic CrtSPARTA. Meanwhile, we also found that tRNA fragments can serve as guide RNAs for SPARTA activation, which probably reveals the origin of the RNA guide for prokaryotic Argonaute. This also suggests the possibility that SPARTA may function cooperatively with other defense systems involving a tRNA endonuclease to efficiently respond to viral infection.
External links	Biochem Biophys Res Commun / PubMed:42172904
Methods	EM (single particle)
Resolution	3.2 - 3.5 Å
Structure data	36592 8jr8 EMDB-36592, PDB-8jr8: MapSPARTA dimer bound with guide-target Method: EM (single particle) / Resolution: 3.48 Å EMDB-37490: Focused map for area 1 of MapSPARTA tetramer bound with guide-target Method: EM (single particle) / Resolution: 3.4 Å EMDB-37496: Focused map for area 2 of MapSPARTA tetramer bound with guide-target Method: EM (single particle) / Resolution: 3.4 Å EMDB-37510: Focused map for area 3 of MapSPARTA tetramer bound with guide-target Method: EM (single particle) / Resolution: 3.2 Å EMDB-37512: Focused map for area 4 of MapSPARTA tetramer bound with guide-target Method: EM (single particle) / Resolution: 3.5 Å EMDB-37608: Raw consensus map of MapSPARTA tetramer bound with guide-target Method: EM (single particle) / Resolution: 3.3 Å 37708 8wp2 EMDB-37708, PDB-8wp2: MapSPARTA tetramer bound with guide-target Method: EM (single particle) / Resolution: 3.3 Å
Source	maribacter polysiphoniae (bacteria)
Keywords	DNA BINDING PROTEIN/DNA/RNA / SPARTA / Ago / Tir / DNA BINDING PROTEIN-DNA-RNA complex / RNA BINDING PROTEIN/DNA/RNA / RNA BINDING PROTEIN-DNA-RNA complex