Assessment of long-range transport potential of polychlorinated Naphthalenes based on three-dimensional QSAR models.

Experimentally determined octanol-air partition coefficients (K OA) for 43 polychlorinated naphthalene (PCN) congeners and experimentally determined subcooled liquid vapor pressures (P L) for 17 PCN congeners were used with comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) to generate three-dimensional quantitative structure-activity relationship (3D-QSAR) models. The data were used to predict K OA values for the other 32 congeners and P L values for the other 58 congeners. The CoMFA and CoMSIA model contour maps showed that the electrostatic fields of the PCN molecules are the most important factors affecting the K OA and P L values. The long-range transport potentials of several PCN homologs were assessed using the following grading system: high mobility (MoCNs), relatively high mobility (DiCNs to TeCNs), relatively low mobility (PeCNs to HeCNs) and low mobility (HeCNs and OCN). The PCN-2 molecule was modified using the contour maps of the two models, and the results showed that introducing an electronegative R1 substituent increased the K OA value but introducing an electropositive R6 substituent decreased the P L value. PCN-2 was in the high mobility class, but introducing these substituents moved the long-range transport potentials of the modified molecules to the relatively high mobility class.

Biphasic regulation of InsP3 receptor gating by dual Ca2+ release channel BH3-like domains mediates Bcl-xL control of cell viability.

Antiapoptotic Bcl-2 family members interact with inositol trisphosphate receptor (InsP3R) Ca(2+)release channels in the endoplasmic reticulum to modulate Ca(2+)signals that affect cell viability. However, the molecular details and consequences of their interactions are unclear. Here, we found that Bcl-xL activates single InsP3R channels with a biphasic concentration dependence. The Bcl-xLBcl-2 homology 3 (BH3) domain-binding pocket mediates both high-affinity channel activation and low-affinity inhibition. Bcl-xL activates channel gating by binding to two BH3 domain-like helices in the channel carboxyl terminus, whereas inhibition requires binding to one of them and to a previously identified Bcl-2 interaction site in the channel-coupling domain. Disruption of these interactions diminishes cell viability and sensitizes cells to apoptotic stimuli. Our results identify BH3-like domains in an ion channel and they provide a unifying model of the effects of antiapoptotic Bcl-2 proteins on the InsP3R that play critical roles in Ca(2+) signaling and cell viability.