Reclinomonas americana

Mitochondrial genome organization, gene content, genetic code

The circular mitochondrial genome of Reclinomonas americana strain ATCC 50394 is 69.034 kbp in size. This genome codes for 97 genes, more than in any other mtDNA known to date (April 1997). There is only one intron (group II), located in the trnW gene. Genes are tightly packed but overlap occurs only in the rpl6-rpl18 and nad10-nad3 gene pairs. Intergenic regions, ca. 8% of the genome, are A+T-rich. Transcribed genes are found on both DNA strands. The standard genetic code is used for translation.

Encoded genes include those commonly found in mtDNA, including the protein-coding genes nad1,2,3,4,4L,5,6, cob, cox1,2,3, and atp6,8,9, as well as large subunit (rnl) and small subunit (rns) rRNA genes and 26 tRNA genes (whose tRNA products are sufficient to recognize all but 1 of the codons in protein-coding sequences). Also present are a number of protein genes typical of protist and plant, but not animal or fungal mtDNAs. These include nad7,9,11, atp1, rpl2,5,6,14,16, and rps2-4,7,8,10-14,19. Three unique ORFs are also encoded by R. americana mtDNA.

A number of R. americana mitochondrial genes are rare or absent in other mitochondrial genomes but are present in bacteria. Among these rare or unique mtDNA-encoded genes are nad8, rpoA-D, rrn5, rnpB, secY, tufA, yejU-W, and several of the ribosomal protein genes.

Vestiges of a prokaryotic operon organization are evident in several gene clusters. For example, there is a close resemblance between the succinate dehydrogenase gene cluster (sdh2-4) in R. americana and the sdh gene cluster in E. coli.

Advocate of this sequencing project: B. F. Lang
Collaborators: C. J. O'Kelly (Bigelow Laboratory for Ocean Sciences), G. Burger
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