Left image: crystal structure of the complex between Mac2 (orange) and Paip1M (light blue). Mac2 possesses a three-layer α/β/α fold. α1, 2, and 3, as well as η1 and α4, 5 form the two outside layers, whereas the β sheet (β3−β4-β2−β5−β6) forms the central layer. The first 16 residues of Mac2 are shown in green. Paip1M comprises ten helices within two layers. α1, 3, 5, 7, and 9 form one layer while α2, 4, 6, 8, and 10 form the other. The long loop region (Ile204−Thr212) is displayed in purple. The N and C termini of Mac2 and Paip1M (in italics) are marked. Right image: space-filling representation showing the tight interaction between Mac2 and Paip1M. 