Fig. 3: Changes in the active site of Cas10 during synthesis of SAM-AMP.
From: Antiviral type III CRISPR signalling via conjugation of ATP and SAM
a, The crystal structure of the P. furiosus (Pfu) Cas10 subunit with 2 bound ATP molecules33. Side chains for the two metal binding aspartate residues of the DD motif, together with residues N300 and R436 that interact with ATP2, are shown. b, Equivalent view of the AF2 model of the B. fragilis (Bfr) Cas10 structure with ATP1 from the P. furiosus Cas10 structure and ATP2 replaced by SAM. The precise conformation and position of SAM is unknown. The conserved acidic residues D70, E151, D328 and D329 are shown. c, In vitro SAM-AMP synthase activity of wild-type and variant B. fragilis Cmr, analysed by HPLC following incubation of 2 µM Cmr with 0.5 mM ATP and SAM for 30 min. Raw HPLC data are presented in Supplementary Data Fig. 3. d, Relative SAM-AMP synthase activity of Cmr variants. Three independent experiments; data are mean ± s.d., calculated using GraphPad Prism 9.
