title: Four inteins and three group II introns encoded in a bacterial ribonucleotide reductase gene.
abstract: A bacterial ribonucleotide reductase gene was found to encode four inteins and three group II introns in the oceanic N2-fixing cyanobacterium Trichodesmium erythraeum. The 13,650-bp ribonucleotide reductase gene is divided into eight extein- or exon-coding sequences that together encode a 768-amino acid mature ribonucleotide reductase protein, with 83% of the gene sequence encoding introns and inteins. The four inteins are encoded on the second half of the gene, and each has conserved sequence motifs for a protein-splicing domain and an endonuclease domain. These four inteins, together with known inteins, define five intein insertion sites in ribonucleotide reductase homologues. Two of the insertion sites are 10 amino acids apart and next to key catalytic residues of the enzyme. Protein-splicing activities of all four inteins were demonstrated in Escherichia coli. The four inteins coexist with three group II introns encoded on the first half of the same gene, which suggests a breakdown of the presumed barrier against intron insertion in this bacterial conserved protein-coding gene.
authors.affiliation: Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia B3H 4H7, Canada. pxqliu@dal.ca
authors.forename: Xiang-Qin
authors.initials: XQ
authors.lastname: Liu
authors.forename: Jing
authors.initials: J
authors.lastname: Yang
authors.forename: Qing
authors.initials: Q
authors.lastname: Meng
mesh_terms: D020816:Amino Acid Motifs; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D017124:Conserved Sequence; D000458:Cyanobacteria / Q000201:enzymology / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D021901:DNA, Intergenic; D007438:Introns; D009690:Nucleic Acid Conformation; D019154:Protein Splicing / Q000235:genetics; D012264:Ribonucleotide Reductases / Q000235:genetics*; D016415:Sequence Alignment
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D021901:DNA, Intergenic; D012264:Ribonucleotide Reductases