Fig. 1.

Crystal structure of BcpA* and topology diagrams of the CNA and XNA domains. (A) The crystal structure of BcpA* was solved using MAD. The CNA₂ and CNA₃ domains are shown as blue ribbons and the XNA domain purple. The Lys and Asn residues forming the intramolecular amide bonds in each of the 3 crystallized domains are shown as red sticks. Topology diagrams of the CNA (B) and XNA (C) domains show the arrangement of β-strands in the reverse Ig-fold (CNA) and jelly-roll fold (XNA). Both CNA₂ and CNA₃ share the same overall topology. β-strands are shown as arrows and α-helices as cylinders. Intramolecular amide bonds are shown as red lines.