Figure 1.

(A) Location of EF hands in the sequence of human calbindin D_28k. Black circle represents the Ca²⁺ ion. Mutation sites are underlined. (B) The EF-hand motifs are shown with high affinity Ca²⁺ sites marked by black circles. Mutant or fragment name is given to the left, with the amino acid identity at each substitution site given to the right. Fragments borders are indicted by numbers inside the bars. (C) List and numbering of the endo-Lys C fragments, as cited in the text, which contain Q and/or N residues and which have molecular weight >700 Da. (D,E) List and numbering of the Asp and chymotrypsin fragments, respectively, which allows the mapping of Q and N inaccessible with Lys-C digestion.