Fig. 1.

Crystal structure of P22 tailspike protein. (A). α-carbon backbone of the C-terminal fragment (1 tsp) (Steinbacher et al. 1994). Each chain is colored from residues 543–579 (blue, red, and green), which include the oligomeric β-helix domain. The α-carbons of residues Gly 546, Arg 563, and Ala 575 are displayed as spheres with van der Waals dimensions. (B) Axial view of the triple β-helix domain from the N terminus toward the C terminus. The coloring scheme is the same as in A. (C) Axial views of the three stacked coils that form the structure in B. Isoleucine and leucine side chains from each subunit can be seen at the center of each coil forming the hydrophobic core of the interdigitated domain. Boxed residues are the sites of substitutions studied in this work. Stars note the positions of these mutations on each chain. Sequences in connecting loops and turns are omitted. The orientation of each view of C is the same as in B.