A MODEL FOR TARGET PROTEIN-BINDING TO CALCIUM-ACTIVATED S100 DIMERS

S100 proteins are a family of dimeric calcium-binding proteins implica ted in several cancers and neurological diseases. Calbindin D-9k is an unusual monomeric member of the S100 family. A calbindin D-9k mutant containing a novel calcium-induced helix is characterized. Based on se quence comparison, this helix could be a component of other S100 prote ins and a factor in target protein binding. The origin of structural d ifferences between three reported apo S100 dimer structures is verifie d. We conclude that the differences are a result of modeling rather th an a function of different target binding properties. A mechanism for target protein binding is suggested. (C) 1998 Federation of European B iochemical Societies.