Figure 1.

Heterologous competition assay revealed that rGIIA and its enzymatically inactive mutant rGIIA(D49S) inhibit ¹²⁵I-Atx binding to its mitochondrial binding protein, CCOX-II. (A) Autoradiogram of the SDS-PAGE gel of detergent extracts of porcine cerebral cortex demyelinated P2 fraction labeled with ¹²⁵I-Atx in the presence of the indicated concentrations of unlabeled sPLA₂s, rGIIA or rGIIA(D49S). The unlabeled sPLA₂s inhibited the formation of the specific adduct with an apparent molecular mass of 39 kDa (black arrows). (B) Dose–response curve relating the extent of cross-linking of ¹²⁵I-Atx with the 25 kDa receptor to the concentration of unlabeled sPLA₂s present during the incubation. The data were obtained by quantifying the intensity of the specific ¹²⁵I-Atx adduct from the autoradiograms in (A).