Fig. 1: Overall structure of Apo SPARTA.
From: Nucleic acid mediated activation of a short prokaryotic Argonaute immune system
a Schematic diagram of the domain architecture of TIR-APAZ and short pAgo. b SDS-PAGE of co-purified short pAgo (58.2 kDa) and TIR-APAZ (53.2 kDa) proteins. Uncropped gel image is provided as a Source Data file. The purification of the SPARTA heterodimer was repeated at least 5 times with similar results. c Mass photometry data of the Apo SPARTA (top) and SPARTA incubated with guide RNA (gRNA) and target DNA (tDNA) heteroduplex (bottom). Apo SPARTA shows a clear homogeneous population for the monomer. Upon incubation with gRNA/tDNA, SPARTA additionally shows the formation of dimer and tetramer complexes. d Crystal structure of TIR-APAZ/short pAgo heterodimeric complex. TIR domain, connector and APAZ domain are colored as green, magenta and orange, respectively. MID, insert57 and PIWI domains of short pAgo are colored as cyan, yellow and slate, respectively. e Structural comparison of monomeric TIR domains from TIR domain in proteins with scaffolding and enzymatic roles. The secondary structure elements are labeled for SPARTA TIR. f Structural comparison of SPARTA APAZ domain with the N-PAZ-L1-L2 regions of the Clostridium butyricum (Cb) long pAgo (PDB ID: 6QZK). The N domain, L1, PAZ, and L2 of CbAgo are colored as olive, orange, light orange and grey, respectively. Based on topological similarity, the APAZ-N, APAZ-L1 and APAZ-L2 of SPARTA APAZ are colored similarly to the CbAgo. g Structural comparison of SPARTA short pAgo with MID and PIWI domains of the Cb long pAgo (PDB ID: 6QZK). The domains are similar in structure with the exception of the presence of Insert57 in SPARTA short pAgo.
