We present a consolidated sequence for part of the linear 15.8 kbp mtDNA of Chlamydomonas reinhardtii, strain CW-15-2 (t277, Duke University Culture Collection).This region (5.15 kbp) contains complete genes for subunit I of cytochrome oxidase (COI) [1] and URF (unassigned reading frame) proteins 2 and 5 (2] (ND2 and ND5, respectively, recently identified as subunits of NADH dehydrogenase [3]), as well as a portion of a fourth gene (ORF x) encoding an unidentified protein [2].The sequence comprises restriction fragments HM, ES2, and E3 (Fig. A).In Fig. B, we compare our sequence with ones recently published by others [4,5] for the same region of another CW-15 strain of C. reinhardtii.Although these sequences display >99% nucleotide identity, there are a number of differences, some of which alter the derived amino acid sequences of the COI and URF 5 proteins.In particular, omission of A618 in [5] results in a truncated URF 5 C-terminal sequence with an atypical codon usage pattern (see [2]).We observe no differences in the URF 2 coding region but we do see one difference downstream (position 5077).Positions 625-626 (GC) and 2272-2276 (TTGGT) were incorrectly reported as CG and CTTGG, respectively, in 121s the nucleotide sequence in (B) now agrees with that in [5] at these positions.Our assignment of initiation codons for the ORF x, URF 5, COI, and URF 2 genes is based on detailed transcript mapping ([2] and ms. in preparation)s for this reason, our sequence of the URF 5 protein lacks the first 21 residues of the URF 5 amino acid sequence proposed in [5].
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Boer et al. (1986) studied this question.