Figure 2

Structures of NCS proteins showing interactions within the exposed hydrophobic groove. (A) Structure of Ca²⁺-bound bovine recoverin with bound N-terminal fragment of rhodopsin kinase including residues 1-25 ([37]; PDB, 2I94). Recoverin is shown in space-filling representation and the rhodopsin kinase is shown in yellow. The rhodopsin kinase fragment forms an α-helix that is embedded in an N-terminal hydrophobic pocket of recoverin. The asterisk indicates the position of the C-terminus of recoverin. (B) Structure of Ca²⁺-bound human KChIP1 showing the binding of the N-terminal residues 3-27 of Kv4.3 ([143, 144]; PDB, 2I2N). KChIP1 is shown in space-filling representation and the Kv4.3 fragment which forms an α-helix shown in yellow is embedded in a hydrophobic groove running across KChIP1. An additional interaction site of Kv4.3 with helix H2 of KChIP1 is omitted for clarity. The asterisk indicates the position of the C-terminus of KChIP1. (C) Structure of of Ca²⁺-bound mouse KChIP4a ([102];PDB, 3DD4) with the structure shown in space-filling representation apart from the N-terminal residues 1-23 which are shown in yellow. The N-terminus forms an α-helix which is embedded within the N-terminal part of the exposed hydrophobic groove of KChIP4a. The asterisk indicates the position of the C-terminus of KChIP4a. (D) Structure of of Ca²⁺-bound S. cerevisiae Frq1 with bound Pik1(121-175) ([142];PDB, 2JU0) the structure of Frq1 is shown in space-filling representation and the Pik1 fragment in yellow. Pik1 forms two α-helices joined by a loop and the helices are bound to the N- and C-terminal parts of a large hydrophobic groove running across Frq1. The asterisk indicates the position of the C-terminus of Frq1. (E) Model for the structure of of Ca²⁺-bound human NCS-1 with two bound molecules of the C-terminal peptide of the D2/D3 receptor. The structure of NCS-1 derived from PDB 1G8I[149] is shown in space-filling representation and the D2/D3 peptides in yellow. The two peptides are bound to the N- and C-terminal parts of the large hydrophobic groove running across Frq1. The asterisk indicates the position of the C-terminus of NCS-1.