66. Papageorgiou AC, Shapiro R, Acharya KR (1997) Molecular recognition of human angiogenin by placental ribonuclease inhibitor—an X-ray crystallo- graphic study at 2.0 A resolution. EMBO J 16: 5162–5177. 67. Kobe B, Deisenhofer J (1996) Mechanism of ribonuclease inhibition by ribonuclease inhibitor protein based on the crystal structure of its complex with ribonuclease A. J Mol Biol 264: 1028–1043. 68. Tan X, Calderon-Villalobos L, Sharon M, Zheng C, Robinson C, et al. (2007) Mechanism of auxin perception by the TIR1 ubiquitin ligase. Nature 446: 640–645. 69. Fan Q, Hendrickson W (2005) Structure of human follicle-stimulating hormone in complex with its receptor. Nature 433: 269–277. 70. Celikel R, McClintock R, Roberts J, Mendolicchio G, Ware J, et al. (2003) Modulation of a-thrombin function by distinct interactions with platelet glycoprotein Iba. Science 301: 218–221. 71. Hao B, Zheng N, Schulman BA, Wu G, Miller JJ, et al. (2005) Structural basis of the Cks1-dependent recognition of p27(Kip1) by the SCF(Skp2) ubiquitin ligase. Mol Cell 20: 9–19. 72. Morlot C, Thielens N, Ravelli R, Hemrika W, Romijn R, et al. (2007) Structural insights into the Slit-Robo complex. Proc Natl Acad Sci U S A 104: 14923–14928. 73. Jin MS, Kim SE, Heo JY, Lee ME, Kim HM, et al. (2007) Crystal structure of the TLR1–TLR2 heterodimer induced by binding of a tri-acylated lipopeptide. Cell 130: 1071–1082. 74. Kang J, Nan X, Jin M, Youn S, Ryu Y, et al. (2009) Recognition of lipopeptide patterns by Toll-like receptor 2-Toll-like receptor 6 heterodimer. Immunity 31: 873–884. 75. Park B, Song D, Kim H, Choi B, Lee H, et al. (2009) The structural basis of lipopolysaccharide recognition by the TLR4–MD-2 complex. Nature 458: 1191–1195. 76. Liu L, Botos I, Wang Y, Leonard J, Shiloach J, et al. (2008) Structural basis of toll-like receptor 3 signaling with double-stranded RNA. Science 320: 379–381. 77. Dickson K, Haigis M, Raines R (2005) Ribonuclease inhibitor: structure and function. Prog Nucl Acid Res Mol Biol 80: 349–374. 78. Dharmasiri N, Dharmasiri S, Estelle M (2005) The F-box protein TIR1 is an auxin receptor. Nature 435: 441–445. 79. Dharmasiri N, Dharmasiri S, Weijers D, Lechner E, Yamada M, et al. (2005) Plant development is regulated by a family of auxin receptor F box proteins. Dev Cell 9: 109–119. Repeat Conservation Mapping 80. Kepinski S, Leyser O (2005) The Arabidopsis F-box protein TIR1 is an auxin receptor. Nature 435: 446–451. 81. Walsh T, Neal R, Merlo A, Honma M, Hicks G, et al. (2006) Mutations in an auxin receptor homolog AFB5 and in SGT1b confer resistance to synthetic picolinate auxins and not to 2, 4-dichlorophenoxyacetic acid or indole-3-acetic acid in Arabidopsis. Plant Physiol 142: 542–552. 82. Zipfel C (2009) Early molecular events in PAMP-triggered immunity. Curr Opin Plant Biol 12: 414–420. 83. Couvreur TL, Franzke A, Al-Shehbaz IA, Bakker FT, Koch MA, et al. (2010) Molecular phylogenetics, temporal diversification, and principles of evolution in the mustard family (Brassicaceae). Mol Biol Evol 27: 55–71. 84. Federici L, Di Matteo A, Ferna´ndez-Recio J, Tsernoglou D, Cervone F (2006) Polygalacturonase inhibiting proteins: players in plant innate immunity? Trends Plant Sci 11: 65–70. 85. Sicilia F, Ferna´ndez-Recio J, Caprari C, De Lorenzo G, Tsernoglou D, et al. (2005) The polygalacturonase-inhibiting protein PGIP2 of Phaseolus vulgaris has evolved a mixed mode of inhibition of endopolygalacturonase PG1 of Botrytis cinerea. Plant Physiol 139: 1380–1388. 86. Dodds PN, Lawrence GJ, Catanzariti AM, Teh T, Wang CI, et al. (2006) Direct protein interaction underlies gene-for-gene specificity and coevolution of the flax resistance genes and flax rust avirulence genes. Proc Natl Acad Sci U S A 103: 8888–8893. 87. Krasileva KV, Dahlbeck D, Staskawicz BJ (2010) Activation of an Arabidopsis resistance protein is specified by the in planta association of its leucine-rich repeat domain with the cognate oomycete effector. Plant Cell 22: 2444–2458. 88. Clark LB, Viswanathan P, Quigley G, Chiang YC, McMahon JS, et al. (2004) Systematic mutagenesis of the leucine-rich repeat (LRR) domain of CCR4 reveals specific sites for binding to CAF1 and a separate critical role for the LRR in CCR4 deadenylase activity. J Biol Chem 279: 13616–13623. 89. Ha¨weker H, Rips S, Koiwa H, Salomon S, Saijo Y, et al. (2010) Pattern recognition receptors require N-glycosylation to mediate plant immunity. J Biol Chem 285: 4629–4636. 90. Binz H, Stumpp M, Forrer P, Amstutz P, Plu¨ ckthun A (2003) Designing repeat proteins: well-expressed, soluble and stable proteins from combinatorial libraries of consensus ankyrin repeat proteins. J Mol Biol 332: 489–503. PLoS ONE | www.plosone.org 14 July 2011 | Volume 6 | Issue 7 | e21614