title: Protein trans-splicing and characterization of a split family B-type DNA polymerase from the hyperthermophilic archaeal parasite Nanoarchaeum equitans.
abstract: Nanoarchaeum equitans family B-type DNA polymerase (Neq DNA polymerase) is encoded by two separate genes, the large gene coding for the N-terminal part (Neq L) of Neq DNA polymerase and the small gene coding for the C-terminal part (Neq S), including a split mini-intein sequence. The two Neq DNA polymerase genes were cloned and expressed in Escherichia coli individually, together (for the Neq C), and as a genetically protein splicing-processed form (Neq P). The protein trans-spliced Neq C was obtained using the heating step at 80 degrees C after the co-expression of the two genes. The protein trans-splicing of the N-terminal and C-terminal parts of Neq DNA polymerase was examined in vitro using the purified Neq L and Neq S. The trans-splicing was influenced mainly by temperature, and occurred only at temperatures above 50 degrees C. The trans-splicing reaction was inhibited in the presence of zinc. Neq S has no catalytic activity and Neq L has lower 3'-->5' exonuclease activity; whereas Neq C and Neq P have polymerase and 3'-->5' exonuclease activities, indicating that both Neq L and Neq S are needed to form the active DNA polymerase that possesses higher proofreading activity. The genetically protein splicing-processed Neq P showed the same properties as the protein trans-spliced Neq C. Our results are the first evidence to show experimentally that natural protein trans-splicing occurs in an archaeal protein, a thermostable protein, and a family B-type DNA polymerase.
authors.affiliation: Department of Genetic Engineering Sungkyunkwan University, 300 Chunchun-Dong Jangan-Ku, Suwon 440-746, South Korea.
authors.forename: Jeong Jin
authors.initials: JJ
authors.lastname: Choi
authors.forename: Ki Hoon
authors.initials: KH
authors.lastname: Nam
authors.forename: Bokkee
authors.initials: B
authors.lastname: Min
authors.forename: Sang-Jin
authors.initials: SJ
authors.lastname: Kim
authors.forename: Dieter
authors.initials: D
authors.lastname: Söll
authors.forename: Suk-Tae
authors.initials: ST
authors.lastname: Kwon
mesh_terms: D000595:Amino Acid Sequence; D019843:Archaeal Proteins / Q000235:genetics* / Q000378:metabolism; D004259:DNA-Directed DNA Polymerase / Q000235:genetics* / Q000378:metabolism; D005090:Exodeoxyribonucleases / Q000378:metabolism; D047668:Inteins / Q000235:genetics; D008969:Molecular Sequence Data; D046588:Nanoarchaeota / Q000235:genetics* / Q000378:metabolism; D016415:Sequence Alignment; D020539:Sequence Analysis, Protein; D013696:Temperature; D020040:Trans-Splicing; D015032:Zinc / Q000378:metabolism
chemical_list: D019843:Archaeal Proteins; D004259:DNA-Directed DNA Polymerase; D005090:Exodeoxyribonucleases; D015032:Zinc