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Evolution of Hyperactive, Repetitive Antifreeze Proteins in Beetles
- Source :
- Journal of Molecular Evolution. 64:387-398
- Publication Year :
- 2007
- Publisher :
- Springer Science and Business Media LLC, 2007.
-
Abstract
- Some organisms that experience subzero temperatures, such as insects, fish, bacteria, and plants, synthesize antifreeze proteins (AFPs) that adsorb to surfaces of nascent ice crystals and inhibit their growth. Although some AFPs are globular and nonrepetitive, the majority are repetitive in both sequence and structure. In addition, they are frequently encoded by tandemly arrayed, multigene families. AFP isoforms from the mealworm beetle, Tenebrio molitor, are extremely potent and inhibit ice growth at temperatures below -5 degrees C. They contain a 12-amino acid repeat with the sequence TCTxSxxCxxAx, each of which makes up one coil of the beta-helix structure. TxT motifs are arrayed to form the ice-binding surface in all three known insect AFPs: the homologous AFPs from the two beetles, T. molitor and Dendroides canadensis, and the nonhomologous AFP from the spruce budworm, Choristoneura fumiferana. In this study, we have obtained the cDNA and genomic sequences of additional T. molitor isoforms. They show variation in the number of repeats (from 6 to 10) which can largely be explained by recombination at various TCT motifs. In addition, phylogenetic comparison of the AFPs from the two beetles suggests that gene loss and amplification may have occurred after the divergence of these species. In contrast to a previous study suggesting that T. molitor genes have undergone positive Darwinian selection (selection for heterogeneity), we propose that the higher than expected ratio of nonsynonymous-to-synonymous substitutions might result from selection for higher AT content in the third codon position.
- Subjects :
- Repetitive Sequences, Amino Acid
Mealworm
media_common.quotation_subject
Molecular Sequence Data
Insect
Crystallography, X-Ray
Protein Structure, Secondary
Evolution, Molecular
Open Reading Frames
Antifreeze protein
Antifreeze Proteins
Complementary DNA
Genetics
Animals
Protein Isoforms
Amino Acid Sequence
Codon
Molecular Biology
Gene
Phylogeny
Ecology, Evolution, Behavior and Systematics
media_common
Base Composition
Likelihood Functions
Base Sequence
Sequence Homology, Amino Acid
biology
Phylogenetic tree
biology.organism_classification
Coleoptera
Choristoneura fumiferana
Amino Acid Substitution
Codon usage bias
Sequence Alignment
Pseudogenes
Subjects
Details
- ISSN :
- 14321432 and 00222844
- Volume :
- 64
- Database :
- OpenAIRE
- Journal :
- Journal of Molecular Evolution
- Accession number :
- edsair.doi.dedup.....419eb8d502441116c560e7618a6a0645