Table 2.

Interhelical angles in EF-hand motifs of different states of Ca2+-regulated photoproteins (degrees)

EF-hand	Aequorin (state II)	Ca2+-loaded apo-aequorin (state V)	Obelin (state II)	Soaked obelin	Ca2+-loaded apo-obelin (state V)	Ca2+-discharged obelin (state IV)
I	70.5	80.6	71.4	73.2	77.4	73.2
II	111.6	106.7	107.3	108.8	108.2	110.9
III	112.2	116.3	111.1	110.5	122.4	111.3
IV	104.3	105.6	106.5	106.1	99.2	106.4

Interhelical angles were calculated using the program interhlx (K. Yap, University of Toronto). Values are based on structures in the following PDB entries: aequorin, 1EJ3 (Head et al. 2000); obelin, 1EL4 (Liu et al. 2000); soaked-obelin, 1QV1 (Liu et al. 2003); Ca²⁺-discharged W92F obelin mutant, 1S36 (Deng et al. 2004b). Photoprotein conformational states II, IV, and V are from Figure 1 ▶.