Ribbon diagram of the predicted ice worm AMPD protein. (a) The M. solifugus AMPD ribbon diagram (green) is superimposed to the A. thaliana -crystal ribbon structure [30] (blue). Double arrowheads point to the large N-terminal transmembrane domain characterizing A. thaliana AMPD; single arrowhead points to the ice worm-specific 16 amino acid loop; the arrow points to the ice worm-specific loop connecting strands and . The catalytic zinc is represented by a yellow sphere, the coformycin -phosphate and phosphate ion are depicted as stick models. (b) A. thaliana -crystal backbone structure [30] depicting 16 ice worm nonconservative species-specific amino acid substitutions, represented by space filling models.