Cloning and characterization of a cDNA encoding a bacteriophage-type RNA polymerase from the higher plant Chenopodium album.
We have cloned a full-length cDNA from the higher plant Chenopodium album coding for a single subunit bacteriophage-type RNA polymerase. The cDNA isolated from an actively growing cell suspension culture recognized a 3.8 kb transcript on Northern blots. The open reading frame comprises 987 amino acids with a predicted molecular mass of 112 kDa. A comparison of the protein sequence with those of the two known fungal mitochondrial RNA polymerases, from Saccharomyces cerevisiae and Neurospora crassa , reveals extensive homology between the three enzymes. with complete conservation of all catalytically essential amino acids. The putative mitochondrial RNA polymerase from C.album , as well as homologous sequences from rice and barley, which have been partially cloned, lack two catalytically non-essential regions of up to 176 amino acids near the C-terminus present in the two fungal mitochondrial RNA polymerases. The extreme N-terminus of the cloned C.album RNA polymerase displays features of a potential mitochondrial transit sequence. In phylogenetic trees constructed to compare the evolutionary relationships between the different single subunit RNA polymerases the C.album sequence forms a subgroup together with the S.cerevisiae and the N.crassa mitochondrial RNA polymerases, well separating from both bacteriophage enzymes and plasmid-encoded RNA polymerases found in mitochondria of many fungi and some higher plants.
Weihe
A
A
Institute of Biology, Humboldt University Berlin, Chausseestrasse 117, D-10115 Berlin, Germany. andreas=weihe@biologire.hu-berlin.de
Hedtke
B
B
Börner
T
T
D000595:Amino Acid Sequence; D001435:Bacteriophages / Q000201:enzymology*; D001483:Base Sequence; D002478:Cells, Cultured; D003001:Cloning, Molecular; D017124:Conserved Sequence; D017931:DNA Primers; D018076:DNA, Complementary; D012321:DNA-Directed RNA Polymerases / Q000096:biosynthesis* / Q000737:chemistry*; D019143:Evolution, Molecular; D008928:Mitochondria / Q000201:enzymology; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009492:Neurospora crassa / Q000201:enzymology; D010802:Phylogeny; D010944:Plants / Q000201:enzymology*; D016133:Polymerase Chain Reaction; D012313:RNA / Q000096:biosynthesis; D000077278:RNA, Mitochondrial; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic
D017931:DNA Primers; D018076:DNA, Complementary; D000077278:RNA, Mitochondrial; D011994:Recombinant Proteins; D012313:RNA; D012321:DNA-Directed RNA Polymerases