Fig. 4
Mechanism of ring closure in Ch-CPN. a Superposition of the open and closed subunits. Major conformational changes are indicated by black dotted circles. b, c Movements of the stem loop and the nucleotide-sensing loop by b AMPPNP (cyan) or c ADP binding (purple). Residues interacting with nucleotides and a magnesium ion are shown in green sticks and a gray sphere, respectively. A black dotted circle indicates the position of the hydrolyzed γ-phosphate represented by P. Movements of the stem loop and the nucleotide-sensing loop are represented by red (in b) and orange (in c) arrows. Residues that are involved in interactions with AMPPNP but do not interact with ADP are indicated in bold underline letters. d Subunit movements on ring closure. On ATP binding, the stem loop is shifted down about 15 Å and concurrently the apical domain moves inwards about 34 Å. e C- and O-interfaces of the closed (upper) and open Ch-CPNs (bottom). Two Leu439 residues in the interface between S1 and S1′ mediate inter ring communication (ball and stick) in the closed state (red) and the open state (blue), respectively. Residues forming the socket are presented as sticks
