Figure 8. SatS has a new fold and hydrophobic grooves that share similarity with the preprotein binding sites of the SecB chaperone.

(A) The overall secondary structure of SatS_C. The hydrophilicity of SatS_C is a colored gradient from cyan (hydrophilic) to maroon (hydrophobic). SatS_C exposes ~2,900 Ų of hydrophobic surface. The predicted primary and secondary polypeptide binding site(s) are delineated. (B) The overall secondary structure of SecB monomer (PDB ID:1QYN) (Dekker et al., 2003). The hydrophilicity of SecB is a colored gradient from cyan (hydrophilic) to maroon (hydrophobic). The primary and secondary client binding site(s) are delineated. Each SecB monomer exposes ~1,900 Ų of hydrophobic surface for client protein interactions (Huang et al., 2016). Molecular graphics and analyses were performed with the UCSF Chimera package (Petersen et al., 2011).

Figure 8—figure supplement 1. SatS_C secondary structure and the predicted secondary structure of SatS_N.

(A) SatS is composed of two domains of similar secondary structure joined by a potential linker of 60 amino acids with little predicted secondary structure. The disordered linker region was predicted using IUPred2A (Mészáros et al., 2018). (B) Multiple sequence alignment of N-domain (SatS_N) with C-domain (SatS_C) without the linker region. Secondary structure elements for each domain are depicted above and below their corresponding sequence. SatS_N has 22% sequence identity (highlighted in red) and 41% sequence similarity to SatS_C (highlighted in yellow and red);TT - tight turn.