Analysis of 76 kb of newly sequenced DNA, located between map positions 182 and 258 kb in the 330-kb chlorella virus PBCV-1 genome, revealed 175 open reading frames (ORFs) of 65 codons or longer. One hundred and five of these 175 ORFs were considered major ORFs. Twenty-one of the 105 major ORFs resembled proteins in databases including ribonucleotide reductase small subunit, RNase III, thioredoxin, glutaredoxin, protein disulfide isomerase, deoxynucleoside kinase, frog virus 3 ATPase, Acetobacter cellulose synthase, a bacteriophage encoded endonuclease, and two C-5 cytosine DNA methyltransferases. One of the ORFs was the PBCV-1 major capsid protein. The 105 major ORFs were evenly distributed along the genome. One set of ORFs was separated by 543 nucleotides whereas 75 of the ORFs were separated by fewer than 100 nucleotides. Nineteen of the 175 ORFs resembled other PBCV-1 ORFs, suggesting that they represent either gene duplications or gene families.
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