Crystal structures of <i>Plasmodium</i> actin I and II.

<p>(<b>A</b>) <i>P. berghei</i> actin II (<i>Pb</i>ActII; yellow) superimposed on α-actin (1eqy <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1004091#ppat.1004091-McLaughlin1" target="_blank">[39]</a>; cyan). (<b>B</b>) <i>P. falciparum</i> actin I (<i>Pf</i>ActI; red) superimposed on α-actin. In both (<b>A</b>) and (<b>B</b>), ATP, subdomains 1–4, and several regions discussed in the text are indicated. Both N and C termini reside in subdomain 1; the N terminus is visible at the front, and the C-terminal helix is on the back side. Note that the C-terminal helix is not visible in actin I. The C-terminal part and the nearby hydrophobic cluster with Trp357 are shown in the zoomed view on the right and the region involved in intra-filament contacts in subdomain 3 in the box at the lower left corner. The blue and pink dots in (<b>B</b>) indicate the approximate positions of the structural elements shown in detail in (<b>C</b>) and (<b>D</b>), respectively. (<b>C</b>) Lys 207 and Glu188 are at an intimate distance in actin I. A similar salt bridge is present between the corresponding residues in latrunculin-bound α-actin, but the hydrogen-bonding distance is longer without the drug. (<b>D</b>) The proline-rich loop with Gly115 in actin I superimposed on that of α-actin. Note the bending of the loop in actin I, due to the more flexible glycine residue.