Evolution of the Antarctic teleost immunoglobulin heavy chain gene.
Notothenioid teleosts underwent major modifications of their genome to adapt to the cooling of the Antarctic environment. In order to identify specific features of the Antarctic teleost immunoglobulin, transcripts encoding the constant region of the IgM heavy chain from 13 Antarctic and non-Antarctic notothenioid species were sequenced. The primary mRNA splicing for the membrane form was found to be atypical in the majority of Antarctic species, because it led to exclusion of two entire constant exons, and to inclusion of 39-nucleotide exons encoding an unusually long Extracellular Membrane-Proximal Domain (EMPD). Genomic DNA analysis revealed that each 39-nucleotide exon fell within a long sequence that was the reverse complement of an upstream region. Deduced amino acid sequence analysis lead to the identification of cysteine encoding codons in the 39-nucleotide exons, but not in the respective sequence counterpart, suggesting that these residues might play an important role in the folding of the EMPD.
Institute of Protein Biochemistry, CNR, Via P. Castellino 111, 80131 Naples, Italy. Electronic address: mr.coscia@ibp.cnr.it.
Maria Rosaria
MR
Coscia
Institute of Protein Biochemistry, CNR, Via P. Castellino 111, 80131 Naples, Italy.
Sonia
S
Varriale
Institute of Protein Biochemistry, CNR, Via P. Castellino 111, 80131 Naples, Italy.
Concetta
C
De Santi
Institute of Protein Biochemistry, CNR, Via P. Castellino 111, 80131 Naples, Italy.
Stefano
S
Giacomelli
Institute of Protein Biochemistry, CNR, Via P. Castellino 111, 80131 Naples, Italy.
Umberto
U
Oreste
D000818:Animals; D001483:Base Sequence; D003080:Cold Temperature; D019295:Computational Biology; D019143:Evolution, Molecular; D005091:Exons; D005399:Fishes / Q000145:classification / Q000235:genetics*; D050438:Genes, Immunoglobulin Heavy Chain; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D007075:Immunoglobulin M / Q000235:genetics; D008957:Models, Genetic; D008958:Models, Molecular; D008969:Molecular Sequence Data; D012326:RNA Splicing; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
D007143:Immunoglobulin Heavy Chains; D007075:Immunoglobulin M