Fig. 1.

(A) Ribbon diagram of the HMk monomer structure. α-Helices are depicted in cyan, β-sheets in green, and coils in orange. Helices are labeled at their N termini as follows: the helices in domain 1, the N-terminal domain, are denoted α1N, α2N, and α3N; the helices in domain 2, the C-terminal domain, are denoted α1C, α2C, and α3C. Note the orange loop connecting the two domains that wraps behind the molecule at about the center of the molecule. Also note the short, parallel β-sheets located at both ends of the long molecular axis. (B) Ribbon diagram of the HMk dimer. α-Helices are depicted in cyan, β-sheets in green, and coils in orange. The four-helix bundle formed by the dimer interface is visible at the top center of the molecule.