1ZDE:
reference: Crystal structures of an intein from the split dnaE gene of Synechocystis sp. PCC6803 reveal the catalytic model without the penultimate histidine and the mechanism of zinc ion inhibition of protein splicing., Sun P, Ye S, Ferrandon S, Evans TC, Xu MQ, Rao Z, J Mol Biol. 2005 Nov 11;353(5):1093-105. Epub 2005 Sep 30. PMID: 16219320

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