Interactions between the components of archaea SRP-mediated protein targeting. Schematic drawing of the coaxially-arranged SRP RNA helices 6 and 8 bound together by SRP19 and two tertiary interactions (dashed lines). The M-domain of the SRP54 protein (dark gray) binds to SRP RNA helix 8 as well as the signal sequence (black). The NG-domains of SRP54 and the FtsY SRP receptor are arranged quasisymmetrically and poised to separate upon the hydrolysis of two G-domain-bound GTP molecules. The N-terminal region labeled A (for acidic) and the C-terminal repeat region (R) of FtsY are variable or may be absent (see Table 2).
