LAUSR

Ultraviolet C (UV‐C) radiation induces apoptosis in mammalian cells via the mitochondrion‐mediated pathway. The Bcl‐2 family of proteins are the regulators of the mitochondrial pathway of apoptosis and appears responsive to UV‐C radiation. It is unknown how the structure and, effectively, the function of these proteins are directly impacted by UV‐C exposure. Here, we present the effect of UV‐C irradiation on the structure and function of pro‐apoptotic Bid‐FL and anti‐apoptotic Bcl‐xlΔC proteins. Using a variety of biophysical tools, we show that, following UV‐C irradiation, the structures of Bcl‐xlΔC and Bid‐FL are irreversibly altered. Bcl‐xLΔC is found to be more sensitive to UV stress than Bid‐FL Interestingly, UV‐C exposure shows dramatic chemical shift perturbations in consequence of dramatic structural perturbations (α‐helix to β‐sheet) in the BH3‐ binding region, a crucial segment of Bcl‐xlΔC. Furter it has been shown that UV‐exposed Bcl‐xlΔC has reduced efficacy of its interactions with pro‐apoptotic tBid.