Carbohydrate-recognition domains fall into multiple fold families.
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Many of these domains are in multidomain proteins that also have other activities.
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Convergent evolution has led to shared features in domains with different folds.
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Families found across the kingdoms of life reflect extensive divergent evolution.
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Polymorphisms that affect sugar binding reflect recent evolutionary pressure.
Protein modules that bind specific oligosaccharides are found across all kingdoms of life from single-celled organisms to man. Different, overlapping and evolving designations for sugar-binding domains in proteins can sometimes obscure common features that often reflect convergent solutions to the problem of distinguishing sugars with closely similar structures and binding them with sufficient affinity to achieve biologically meaningful results. Structural and functional analysis has revealed striking parallels between protein domains with widely different structures and evolutionary histories that employ common solutions to the sugar recognition problem. Recent studies also demonstrate that domains descended from common ancestors through divergent evolution appear more widely across the kingdoms of life than had previously been recognized.
