Larger Image Fig. 2. Structure and function of the CCT complex, selection analyses on CCTα, and comparison of local stability values from CCTα apical domain between shallow and deep species. (A) Model of tertiary structure of the CCTα subunit. Each subunit is composed of an apical domain (AD; green) containing the substrate-binding regions (PL: proximal loop; AH: apical hinge; H11: Helix 11), an intermediate domain (ID; blue) and an equatorial domain (ED; pink) containing the ATP-binding sites and where hydrolysis takes place. (B) Model of the top view of the CCT complex, encompassing eight paralogous subunits. (C) Quaternary structure model of the CCT complex encompassing a double ring of eight paralogous subunits. (D) Simplified model of prefoldin (PFD)-CCT interaction in the folding of newly synthesized actin or tubulin. (A–D) Adapted from Bueno-Carrasco and Cuéllar (2018). (E) Localization of the positively selected sites on the tertiary structure of CCTα in the four ophiuroid families investigated. (F) Average protein stability profiles and respective standard deviations (vertical bars) for each codon of the CCTα apical domain in 324 species (424 individuals) from shallow water (0–200 m; in black) and 401 species (543 individuals) from deep water (>200 m; in blue) representative of the whole ophiuroid class. A smaller (i.e., more negative) value of ΔG is indicative of substitutions increasing stability. The substrate-binding regions PL, AH, and H11 are highlighted as well as the positively selected sites. Image published in: Weber AA et al. (2020) Image downloaded from an Open Access article in PubMed Central. © The Author(s) 2020 Permanent Image Page Printer Friendly View ECB-IMG-189932