Recognition of human tumor necrosis factor ? (TNF-?) by therapeutic antibody fragment: energetics and structural features.

ABSTRACT: Human tumor necrosis factor ? (TNF-?) exists in its functional state as a homotrimeric protein and is involved in inflammation processes and immune response of a human organism. Overproduction of TNF-? results in the development of chronic autoimmune diseases that can be successfully treated by inhibitors such as monoclonal antibodies. However, the nature of antibody-TNF-? recognition remains elusive due to insufficient understanding of its molecular driving forces. Therefore, we studied the energetics of binding of a therapeutic antibody fragment (Fab) to the native and non-native forms of TNF-? by employing calorimetric and spectroscopic methods. Global thermodynamic analysis of data obtained from the corresponding binding and urea-induced denaturation experiments has been supported by structural modeling. We demonstrate that the observed high affinity binding of Fab to TNF-? is an enthalpy-driven process due mainly to specific noncovalent interactions taking place at the TNF-?-Fab binding interface. It is coupled to entropically unfavorable conformational changes and accompanied by entropically favorable solvation contributions. Moreover, the three-state model analysis of TNF-? unfolding shows that at physiological concentrations, TNF-? may exist not only as a biologically active trimer but also as an inactive monomer. It further suggests that even small changes of TNF-? concentration could have a considerable effect on the TNF-? activity. We believe that this study sets the energetic basis for understanding of TNF-? inhibition by antibodies and its unfolding linked with the concentration-dependent activity regulation.

SUBMITTER: Marusic J 

PROVIDER: S-EPMC3318754 | biostudies-literature | 2012 Mar

REPOSITORIES: biostudies-literature