Cloning and sequencing of cDNAs of the β-globin gene family in carp

A total blood cell cDNA library was constructed using a 3-year-old carp Cyprinus carpio. A beta -globin cDNA (C beta G1) was identified from the library by the polymerase chain reaction using a beta -globin-specific primer deduced from the carp beta -globin-A amino acid sequence. Also, five additional types of beta -globin cDNAs (C beta G2 similar to 6) were isolated by colony hybridization using C beta G1 as a probe. Sequence analysis revealed that these C beta Gs encoded 147 amino acids, and the deduced amino acid sequences showed high identity (89 times 1-95 times 2%) to previously reported carp beta -globin amino acid sequences. The nucleotide sequences of the C beta Gs were very similar (identity 96 times 0-99 times 6%) and the expression levels of C beta G1 similar to 6 were 28 times 6, 28 times 6, 21 times 4, 14 times 3, 3 times 6 and 3 times 6% of the total number of cloned C beta Gs, respectively. Although the complete amino acid sequence identities between the C beta Gs and the beta -globin of higher vertebrates were low, functionally important regions such as the alpha - beta contact region and haem contact region were well conserved. These data showed that, as in higher vertebrates, the adult carp has a multiple beta -globin gene family (at least six members). However, transcripts encoding four types of peptides (C beta G1 type, C beta G2 and 3 type, C beta G5 type, and C beta G4 and 6 type) were expressed at relatively high levels, this being a unique character of the carp haemoglobin system.