PROTEIN TRANSSPLICING BY A SPLIT INTEIN ENCODED IN A SPLIT DNAE GENE OF SYNECHOCYSTIS SP. PCC6803

A split intein capable of protein trans-splicing is identified in a Dn aE protein of the cyanobacterium Synechocystis sp, strain PCC6803. The N- and C-terminal halves of DnaE (catalytic subunit alpha of DNA poly merase In) are encoded by two separate genes, dnaE-n. and dnaE-c, resp ectively, These two genes are located 745,226 bp apart in the genome a nd on opposite DNA strands. The dnaE-n product consists of a N-extein sequence followed by a 123-aa intein sequence, whereas the dna-c produ ct consists of a 36-aa intein sequence followed by a C-extein sequence . The N- and C-extein sequences together reconstitute a complete DnaE sequence that is interrupted by the intein sequences inside the beta- and tau-binding domains. The two intein sequences together reconstitut e a split mini-intein that not only has intein-like sequence features but also exhibited protein tr trans-splicing activity when tested in E scherichia coli cells.