In this paper we introduce the notion of protein interaction network. This is a graph whose vertices are the protein-s amino acids and whose edges are the interactions between them. Using a graph theory approach, we observe that according to their structural roles, the nodes interact differently. By leading a community structure detection, we confirm this specific behavior and describe thecommunities composition to finally propose a new approach to fold a protein interaction network., {"references":["R. Albert, H. Jeong, and A.-L. Barab'asi. The diameter of the world wide web. Nature, 401:130-131, 1999.","A. R. Atilgan, P. Akan, and C. Baysal. Small-world communication of residues and significance for protein dynamics. Biophys J, 86(1 Pt\n1):85-91, January 2004.","R. Beatson and L. Greengard. A short course on fast multipole methods.","H. M. Berman, J. Westbrook, Z. Feng, G. Gilliland, T. N. Bhat,\nH. Weissig, I. N. Shindyalov, and P. E. Bourne. The protein data bank. Nucleic Acids Research, 28:235-242, 2000.","C. Branden and J. Tooze. Introduction to protein structure. Garland\nPublishing, 1999.","K. V. Brinda and S. Vishveshwara. A network representation of protein\nstructures: implications for protein stability. Biophys J, 89(6):4159-\n4170, December 2005.","A. Broder, R. Kumar, F. Maghoul, P. Raghavan, S. Rajagopalan, R. Stata,\nA. Tomkins, and J. Wiener. Graph structure in the Web. Computer Networks, 33(1-6):309-320, 2000.","Aaron Clauset, M. E. J. Newman, and Cristopher Moore. Finding\ncommunity structure in very large networks. Physical Review E,\n70:066111, 2004.","N. V. Dokholyan, L. Li, F. Ding, and E. I. Shakhnovich. Topological\ndeterminants of protein folding. Proc Natl Acad Sci U S A, 99(13):8637-\n8641, June 2002.\n[10] Thomas M. J. Fruchterman and Edward M. Reingold. Graph drawing\nby force-directed placement. Software - Practice and Experience,\n21(11):1129-1164, 1991.\n[11] O. Gaci and S. Balev. Hubs identification in amino acids interaction\nnetworks. In Proceedings of the 7th ACS/IEEE International Conference\non Computer Systems and Applications, 2009. 7 pages.\n[12] O. Gaci and S. Balev. The small-world model for amino acid interaction\nnetworks. In Proceedings of the IEEE AINA 2009, workshop on\nBioinformatics and Life Science Modeling and Computing, 2009. 6\npages.\n[13] A. Ghosh, K. V. Brinda, and S. Vishveshwara. Dynamics of lysozyme\nstructure network: probing the process of unfolding. Biophys J,\n92(7):2523-2535, April 2007.\n[14] L. Greengard and V. Rokhlin. A fast algorithm for particle simulations.\nJ. Comput. Phys., 73(2):325-348, 1987.\n[15] H. Jeong, B. Tombor, R. Albert, Z. N. Oltvai, and A.-L. Barab'asi. The\nlarge-scale organization of metabolic networks. Nature, 407(6804):651-\n654, October 2000.\n[16] U. K. Muppirala and Z. Li. A simple approach for protein structure\ndiscrimination based on the network pattern of conserved hydrophobic\nresidues. Protein Eng Des Sel, 19(6):265-275, June 2006.\n[17] M. E. J. Newman. Fast algorithm for detecting community structure in\nnetworks. Physical Review E, 69:066133, 2004.\n[18] John P. Scott. Social Network Analysis: A Handbook. SAGE Publications,\nJanuary 2000.\n[19] S. Wasserman and K. Faust. Social network analysis : methods and\napplications , volume 8 of Structural analysis in the social sciences.\nCambridge University Press, Cambridge, 1994.\n[20] D. J. Watts and S. H. Strogatz. Collective dynamics of -small-world-\nnetworks. Nature., 393:440-442, 1998.\n[21] Bo Yang and Da You Liu. Incremental algorithm for detecting community structure in dynamic networks. In proceedings of the 4th International Conference on Machine Learning and Cybernetics, pages 2284-2290, August 2005."]}