Now on display: a gallery of group II intron structures at different stages of catalysis

Table 1 Available 3-D X-ray structures of the group II intron

PDB id	Resolution (Å)	Metals	Splicing stage	Activity	Construct	Reference
4DS6	3.64	NH₄⁺/Mg²⁺	5′-exon hydrolysis (pre)	No (active site mutant)	OiD1-6-G359A	[29]
4FAQ	3.11	K⁺/Ca²⁺	5′-exon hydrolysis (pre)	No (nonfunctional divalent ion)	Oi5eD1-5	[30]
4FAR	2.86	K⁺/Mg²⁺	5′-exon hydrolysis (post)	Yes	Oi5eD1-5	[30]
4FAU	2.87	Li⁺/Mg²⁺	Intermediate	Partial (nonfunctional monovalent ion)	Oi5eD1-5	[30]
3IGI^a	3.13	K⁺/Mg²⁺	Postcatalytic ligand-bound	Yes	OiD1-6	[26, 27]
4E8M	3.50	K⁺/Mg²⁺	Ligand-free	Yes	OiD1-5	[30]
4E8P	3.28	Rb⁺/Mg²⁺	Ligand-free	Yes	OiD1-5	[30]
4E8R	3.36	Cs⁺/Mg²⁺	Ligand-free	Partial (nonfunctional monovalent ion)	OiD1-5	[30]
4E8Q	2.84	Tl⁺/Mg²⁺	Ligand-free	Yes	OiD1-5	[30]
4E8N	2.96	NH₄⁺/Mg²⁺	Ligand-free	Yes	OiD1-5	[30]
4E8V	3.99	K⁺/Ba²⁺	Ligand-free	No (nonfunctional divalent ion)	OiD1-5	[30]
4FAX	3.10	Na⁺/Mg²⁺	Ligand-free	No (nonfunctional monovalent ion)	OiD1-5	[30]
4FB0	3.22	K⁺/Mg²⁺	Ligand-free	Partial (active site mutant)	OiD1-5-C377G	[30]
4E8K^b	3.03	K⁺/Ca²⁺	SER (pre)	No (nonfunctional divalent ion)	OiD1-5	[30]
4E8T	3.34	K⁺/Ca²⁺	SER (pre)	No (nonfunctional divalent ion)	OiD1-5	[30]
4FAW	2.70	K⁺/Mg²⁺	SER (post)	Yes	OiD1-5	[30]

^a Additional PDB entries 3BWP, 3EOH and 3G78 represent the same form of the group II intron in the state following 3′-exon hydrolysis as 3IGI, which results from the most recent refinement. These depositions were obtained by applying different integration and refinement procedures against the same set of experimental crystallographic data.
^b PDB entry 3EOG represents the same form of the group II intron in the state preceding the SER reaction as 4E8K, but was solved at a lower resolution (3.39 Å) using construct OiD1-6 [31].
PDB: Protein Data Bank.

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