The (QxW)3 domain: a flexible lectin scaffold.

Lectins form a class of proteins that have evolved a specialized carbohydrate-binding function. Based on amino acid sequence analysis, several lectin families have been described and a lectin domain, the (QxW)3 domain, was discussed recently based on 11 family members. In this paper, the (QxW)3 domain family is extended to 45 sequences, several of which have very low sequence identity with the previously known members of the family. A hidden Markov model was used to identify the most divergent members of the family. The expanded set of sequences gives us a more complete appreciation of the conserved features, and the lack thereof, in this lectin family. This, in turn, provides new insights in the structural and functional properties of the individual family members.