title: An unusual region of Paramecium mitochondrial DNA containing chloroplast-like genes.
abstract: Based on DNA and amino acid comparisons with known genes and their products, a region of the Paramecium aurelia mitochondrial (mt) genome has been found to encode the following gene products: (1) photosystem II protein G (psbG); (2) a large open reading frame (ORF400) which is also found encoded in the chloroplast (cp) DNA of tobacco (as ORF393) and liverwort (as ORF392), and in the kinetoplast maxicircle DNA of Leishmania tarentolae (as ORFs 3 and 4); (3) ribosomal protein L2 (rpl2); (4) ribosomal protein S12 (rps12); (5) ribosomal protein S14 (rps14); and (6) NADH dehydrogenase subunit 2 (ndh2). All of these genes have been found in cp DNA, but the psbG gene has never been identified in a mt genome, and ribosomal protein genes have never been located in an animal or protozoan mitochondrion. The ndh2 gene has been found in both mitochondria and plastids. The Paramecium genes are among the most divergent of those sequenced to date. Two of the genes are encoded on the strand of DNA complementary to that encoding all other known Paramecium mt genes. No gene contains an identifiable intron. The rps12 and psbG genes are probably overlapping. It is not yet known whether these genes are transcribed or have functional gene products. The presence of these genes in the mt genome raises interesting questions concerning their evolutionary origin.
authors.affiliation: Department of Microbiology and Immunology, University of Colorado Health Sciences Center, Denver 80262.
authors.forename: A E
authors.initials: AE
authors.lastname: Pritchard
authors.forename: S E
authors.initials: SE
authors.lastname: Venuti
authors.forename: M A
authors.initials: MA
authors.lastname: Ghalambor
authors.forename: C L
authors.initials: CL
authors.lastname: Sable
authors.forename: D J
authors.initials: DJ
authors.lastname: Cummings
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D002734:Chlorophyll / Q000235:genetics; D002736:Chloroplasts; D004272:DNA, Mitochondrial / Q000235:genetics*; D045342:Light-Harvesting Protein Complexes; D008969:Molecular Sequence Data; D010247:Paramecium / Q000235:genetics*; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D010940:Plant Proteins / Q000235:genetics; D015183:Restriction Mapping; D012269:Ribosomal Proteins / Q000235:genetics
chemical_list: D004272:DNA, Mitochondrial; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D012269:Ribosomal Proteins; C029466:ribosomal protein L2; C034212:ribosomal protein S12; C039747:ribosomal protein S14; D002734:Chlorophyll