Molecular adaptation of a leaf-eating bird: stomach lysozyme of the hoatzin |
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Authors: | Kornegay JR; Schilling JW; Wilson AC |
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Institution: | Department of Molecular and Cell Biology, University of California, Berkeley 94720. |
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Abstract: | This report describes a lysozyme expressed at high levels in the stomach of
the hoatzin, the only known foregut-fermenting bird. Evolutionary
comparison places it among the calcium-binding lysozymes rather than among
the conventional types. Conventional lysozymes were recruited as digestive
enzymes twice in the evolution of mammalian foregut fermenters, and these
independently recruited lysozymes share convergent structural changes
attributed to selective pressures in the stomach. Biochemical convergence
and parallel amino acid replacements are observed in the hoatzin stomach
lysozyme even though it has a different genetic origin from the mammalian
examples and has undergone more than 300 million years of independent
evolution.
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Keywords: | |
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