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QSAR models for a diverse set of compounds for cytochrome P450 1A2 inhibition have been produced using 4 statistical approaches; partial least squares (PLS), multiple linear regression (MLR), classification and regression trees (CART), and bayesian neural networks (BNN). The models complement one another and have identified the following descriptors as important features for CYP1A2 inhibition; lipophilicity, aromaticity, charge, and the HOMO/LUMO energies. Furthermore all models are global and have been used to predict a diverse independent set of compounds. For the first time in the field of QSAR, the kappa index of agreement has comprehensively been used to assess the overall accuracy of the model's predictive power. The models are statistically significant and can be used as a rapid computational filter for cytochrome P450 1A2 inhibition potential of compound libraries.

Cdc42Hs is a member of the Ras superfamily of GTPases and initiates a cascade that begins with the activation of several kinases, including p21-activated kinase (PAK). We have previously used a 46 amino acid fragment of PAK (PBD46) to define the binding surface on Cdc42Hs [Guo et al. (1998) Biochemistry 37, 14030-14037]. Here we describe the three-dimensional solution structure of the Cdc42Hs. GMPPCP-PBD46 complex. Heteronuclear NMR methods were used to assign resonances in the complex, and approximately 2400 distance and dihedral restraints were used to calculate a set of 20 structures using a combination of distance geometry, simulated annealing, and chemical shift and Ramachandran refinement. The overall structure of Cdc42Hs in the complex differs from the uncomplexed structure in two major aspects: (1) the first alpha helix is reoriented to accommodate the binding of the peptide and (2) the regions corresponding to switch I and switch II are less disordered. As suggested by our previous work (Guo et al., 1998) and similar to the complex between Cdc42Hs and fACK [Mott et al. (1999) Nature 399, 384-388], PBD46 forms an intermolecular beta-sheet with beta2 of Cdc42Hs and contacts both switch I and switch II. The extensive binding surface between PBD46 and Cdc42Hs can account for both the high affinity of the complex and the inhibition by PBD46 of GTP hydrolysis.