AbstractsBiology & Animal Science

The last few decades have witnessed an upsurge in the availability of large-scale data on genomes and genome-scale information. The development of methods to understand the trends and patterns from large scale data promised potentially to unravel the mechanisms responsible for the enormous diversity observed in biological systems. Of the many mechanisms adopted, protein-protein interactions represent one of the commonly adopted mechanisms to achieve functional diversity using a limited genetic repertoire. Protein-proteins interactions bring about several fundamental cellular processes and also modulate regulation at the cellular level. Different types of protein-protein interactions have evolved to carry out myriad functions in a cell. Mainly, interactions can be permanent or transient in nature, depending on the duration of interaction. In terms of affinity ,they are classified as obligate or non-obligate interactions. Structural studies on the various kinds of complexes have enabled the identification of the distinctive features characterizing the different types of complexes. Further, identifying the mechanisms involved in the evolution of protein-protein interactions are important in understanding the forces involved in their maintenance. Such studies also provide clues for the development of methods to predict protein-protein interactions from the large repertoire of sequence and structural data available. In spite of significant understanding of various aspects of protein-protein interactions, several questions still remain unanswered. The work embodied in this thesis studies two main aspects of protein-protein interactions for various types of complexes: structural and evolutionary features. The first part of the thesis(comprising of chapters 2,3,4 and 5) involves structural studies on the following features of protein-protein interactions: structural change, flexibility, symmetry, and residue conservation. The second part of the thesis(comprising of chapters 6,7,8 and 9) involves study of evolutionary aspects of protein-protein interactions, based on both large-scale data as well as case studies. Chapter1 provides a background and literature survey of the area of protein-protein interactions. The different classification schemes commonly used for describing the various protein-protein interactions are outlined. The key small-scale and large-scale experimental methods used for the identification of protein-protein interactions are described along with the details of the databases storing such experimentally derived information. Further, a comprehensive account of structural and evolutionary studies performed so far using the available data is provided. The computational(prediction)methods developed to address various aspects of protein-protein interactions are also outlined. In addition, the importance of protein-protein interactions in the context of diseases and the development of methods used to inhibit these interactions are discussed. Finally, the efforts towards design of protein-protein interactions…