Sequestration of critical nutrients (such as Zn(II), Fe(II) and Mn(II)) during pathogenic invasion is a common strategy undertaken by host cells to thwart infection. In humans, this task is performed by a subset of Ca(II) binding S100 proteins such as S100A12. By chelating Zn(II) at its dimeric interface, S100A12 performs antimicrobial activities. During infection, S100A12 interacts with membrane receptors such as the receptor for advanced glycation end products (RAGE) to initiate a pro-inflammatory signaling cascade. Although known to participate in both antimicrobial and pro-inflammatory activities, the mode of interaction of S100A12 with membrane receptors that initiates inflammatory signaling, is not known. Our research program envisions investigating molecular-level interactions of S100A12 that instigate inflammatory pathways. Our recently reported studies have identified several key features of S100A12 such as (i) the ability of the protein to form reversible oligomeric assemblies that is mostly dominated by Zn(II) binding; (ii) Zn(II) ligation introduced conformational changes to functionally relevant domains of the protein and; (iii) the modulation of Zn(II) sequestration by Ca(II) at physiologically relevant pH conditions. These results, along with previously reported studies in the literature demonstrating the presence of oligomeric S100A12 at inflammatory sites in vivo have laid the foundation of our hypothesis which proposes a metal binding mediated crosstalk between antimicrobial and inflammatory functions of S100A12. Our research program will undertake a biophysical approach to investigate molecular level interactions of S100A12 that afford its functions in the immune response. Focusing on divalent metal ion (Ca(II) and Zn(II)) binding and their influence on S100A12 functions, we propose the following specific aims to test our hypothesis: (i) calcium induced regulation of structure, dynamics and functions; (ii) divalent metal ion mediated signal transduction by S100A12; and (iii) molecular basis of S100A12 interactions in inflammatory responses. These proposed studies will focus on the role of Ca(II) and Zn(II) binding to atomic- and molecular-level details to evaluate the factors influencing S100A12-membrane sensor interactions in vitro. The findings of our work are expected to provide a framework for overall functioning of similar immune system components, allowing for the development of a generalized model of the immune response. Lastly, this work is also expected to generate information that could help develop efficient therapeutic targeting molecules such as S100A12 during aberrant inflammation.