Molecular cloning and novel repeated sequences of a C-type lysozyme gene in Japanese flounder (Paralichthys olivaceus)

A clone of a DNA fragment of approximately 10 kb that included a c-type lys ozyme gene of Japanese flounder (Paralichthys olivaceus) was isolated from a Japanese flounder genomic DNA library. This clone was subcloned, and the nucleotide sequence of the c-type lysozyme gene was determined. The flounde r c-type lysozyme gene, which consisted of 3,617 bp, was found to be compos ed of four exons and three introns. The transcription start Site was determ ined to be 44 bp upstream of the ATG codon by primer extension analysis. Th e number of exons and introns and the positions of the catalytic residues o f the flounder gene were the same as those of the human and chicken c-type lysozyme genes. However, introns 1 and 3 of the flounder gene were shorter, and intron 2 was longer, than those in the other reported vertebrates gene s. There were no Alu repeated sequences in the flounder lysozyme gene, as d etermined for the human lysozyme gene, but 45 repeated sequences were found in the second intron of the flounder lysozyme gene. We suggest that the le ngth of intron 2 in the Japanese flounder c-type lysozyme gene depends on t he presence of this repeated sequence. Furthermore, Southern blot analysis revealed that the c-type lysozyme gene was probably a single copy in the ge nomic DNA of home-cloned Japanese flounder.