Figure 1. Structure of monomeric actin.

(A) Subdomain arrangement. Subdomains 1, 2, 3 and 4 are shown in cyan, red, yellow and green, respectively. The pink sphere represents Mg²⁺ at the active site. (B) Positions of substituted residues in C. yaquinae actin as compared to rabbit/chicken actin. The residues shown in red and cyan in the licorice model represent the specific substitutions in deep-sea fish actins and those of terrestrial animals and shallow-water fish species, respectively. (C) Chemical formula of ATP. Oxygen atoms in the phosphate tail of ATP are distinguished by α, β, and γ.