Transfer RNA genes and the genetic code in Chlamydomonas reinhardtii mitochondria |
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Authors: | Poppo H Boer Michael W Gray |
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Institution: | (1) Department of Biochemistry, Dalhousie University, B3H 4H7 Halifax, Nova Scotia, Canada;(2) Present address: Department of Medicine, University of Ottawa, KlH 8M5 Ottawa, Ontario, Canada |
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Abstract: | Summary Only three tRNA genes are present within a sequenced 12.35 kbp region of the 15.8 kbp mtDNA of Chlamydomonas reinhardtii, a unicellular green alga. The corresponding tRNAs, whose anticodons are specific for TGG (Trp), CAA/G (Gln) and ATG (Met) codons, all display conventional secondary structures. The tRNAMet gene encodes an elongator rather than initiator species. The standard genetic code is used in C. reinhardtii mitochondria, but codon distribution is highly biased: in a collection of six identified protein coding genes, nine codons (including TGA) are not used at all, while four other sense codons occur very infrequently. In spite of the absence of certain codons, a minimum of 23 tRNAs (assuming separate initiator and elongator tRNAsMet are used) is needed to translate the C. reinhardtii mitochondrial genetic code. It appears unlikely that this minimal tRNA set is encoded by C. reinhardtii mtDNA. |
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Keywords: | tRNA genes Genetic code Mitochondria Chlamydomonas reinhardtii |
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