Figure 2.

(A) Structure-guided multiple sequence alignment of the fibropellins (SpEGFI and SpEGFIII) avidin-like domain, avidin, and streptavidin. The top line of each aligned block relates secondary structure information (E, β-strand). The bottom line identifies those residues that are within 4.5 Å to the bound biotin in both streptavidin and avidin (•, conserved with the fibropellins; ▴, nonconserved). Only the backbone of the chain is proximate to biotin in the position including V37 of avidin. (B) Structural model for the avidin-like domain of fibropellin. The binding site is blocked by glutamic acid 35 (left) and arginine 65 (right), shown space-filled. Biotin is shown in “ball-and-stick” mode. The figure was prepared using Molscript (Kraulis 1991).