Split dnaE genes encoding multiple novel inteins in Trichodesmium erythraeum.
Three inteins were found when analyzing a pair of split dnaE genes encoding the catalytic subunit of DNA polymerase III in the oceanic N2-fixing cyanobacterium Trichodesmium erythraeum. The three inteins (DnaE-1, DnaE-2, and DnaE-3) were clustered in a 70-amino acid (aa) region of the predicted DnaE protein. The DnaE-1 intein is 1258 aa long and three times as large as a typical intein, due to the presence of large tandem repeats in which a 57-aa sequence is repeated 17 times. The DnaE-2 intein has a more typical size of 428 aa with putative protein splicing and endonuclease domains. The DnaE-3 intein is a split intein consisting of a 102-aa N-terminal part and a 36-aa C-terminal part encoded on the first and second split dnaE genes, respectively. Synthesis of a mature DnaE protein is predicted to involve expression of two split dnaE genes followed by two protein cis-splicing reactions and one protein trans-splicing reaction. Tandem repeats in the DnaE-1 intein inhibited the protein splicing activity of this intein when tested in Escherichia coli cells and may potentially regulate DnaE synthesis in vivo.
Liu
Xiang-Qin
XQ
Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, Nova Scotia B3H 4H7, Canada. pxqliu@dal.ca
Yang
Jing
J
D000595:Amino Acid Sequence; D001483:Base Sequence; D000458:Cyanobacteria / Q000201:enzymology* / Q000235:genetics*; D004258:DNA Polymerase III / Q000235:genetics*; D004269:DNA, Bacterial / Q000235:genetics; D015870:Gene Expression; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D019154:Protein Splicing; D017386:Sequence Homology, Amino Acid; D020080:Tandem Repeat Sequences
D004269:DNA, Bacterial; C074904:DNA polymerase III, alpha subunit; D004258:DNA Polymerase III