Specific Characteristics of the Conserved Region of Partial cDNA Clone of Transferrin Gene of an Air-breathing Snakehead, Channa gachua (Hamilton)

By immunoblotting against rabbit anti-TF antisera, a clone showing sequence homology with N- and C- lobes of conserved region of teleost transferrin genes has been isolated from cDNA library constructed from liver mRNA of air-breathing murrel, Channa gachua. The sequence, though partial, exhibits several features characteristic to this murrel, which belongs to a highly specialized group of teleosts. The cloned insert is a 483-nucleotide fragment with a deduced amino acid sequence of 161 residues. The pri-mary sequence displays species specific positioning of two cysteine residues and a stretch of 30 tandem asparagine residues. The asparagine stretch suggests the existence of an unstable region, unique to C. gachua and unreported for a fish serotransferrin. In addi-tion, the sequence is also more AT-rich than any of the accessed sequences of the teleost TF. Some differences between the polar, hydrophobic and acidic interactions are also indicated. Percentage of identity and positives of C. gachua clone in TF sequences of several other fish taxons suggests a descent from specialized lineage.