Nucleotide sequence of the cox3 gene from Chondrus crispus: evidence that UGA encodes tryptophan and evolutionary implications

Nucleic Acids Res. 1994 Apr 25;22(8):1400-3. doi: 10.1093/nar/22.8.1400.


We present the nucleotide sequence of the gene encoding subunit 3 of cytochrome c oxidase in Chondrus crispus, the first report on a mitochondrial gene from a red alga. Amino acid alignment with homologous proteins shows that tryptophan is specified by UGA, as in the mitochondrial code of most organisms other than green plants. However, phylogenetic analyses of cox3 amino acid and nucleotide sequences indicate that C. crispus COX3 is related to the green-plant mitochondrial lineage. No RNA editing was detected on the corresponding transcript. As the only known photosynthetic eukaryotes that both share an immediate mitochondrial ancestor with green plants and exhibit features characteristic of non-plant mitochondria, ie, a small-sized mitochondrial genome and a modified genetic code, rhodophytes may be thought of as an intermediate evolutionary link at the root of the green-plant mitochondrial lineage.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Biological Evolution*
  • Codon*
  • DNA, Mitochondrial
  • Electron Transport Complex IV / genetics*
  • Humans
  • Mitochondria / enzymology
  • Molecular Sequence Data
  • Rhodophyta / enzymology
  • Rhodophyta / genetics*
  • Sequence Homology, Amino Acid
  • Tryptophan / genetics*


  • Codon
  • DNA, Mitochondrial
  • Tryptophan
  • Electron Transport Complex IV

Associated data

  • GENBANK/J01415
  • GENBANK/M10217
  • GENBANK/M68929
  • GENBANK/P24879
  • GENBANK/X00668
  • GENBANK/X03240
  • GENBANK/X04764
  • GENBANK/X16868
  • GENBANK/X52539
  • GENBANK/Z29482