Vascular endothelial growth factor receptor KDR tyrosine kinase activity is increased by autophosphorylation of two activation loop tyrosine residues.

Vascular endothelial growth factor is an important physiological regulator of angiogenesis. The function of this endothelial cell selective growth factor is mediated by two homologous tyrosine kinase receptors, fms-like tyrosine kinase 1 (Flt-1) and kinase domain receptor (KDR). Although the functional consequence of vascular endothelial growth factor binding to the Flt-1 receptor is not fully understood, it is well established that mitogenic signaling is mediated by KDR. Upon sequencing several independent cDNA clones spanning the cytoplasmic region of human KDR, we identified and confirmed the identity of a functionally required valine at position 848 in the ATP binding site, rather than the previously reported glutamic acid residue, which corresponds to an inactive tyrosine kinase. The cytoplasmic domain of recombinant native KDR, expressed as a glutathione S-transferase fusion protein, can undergo autophosphorylation in the presence of ATP. In addition, the kinase activity can be substantially increased by autophosphorylation at physiologic ATP concentrations. Mutation analysis indicates that both tyrosine residues 1054 and 1059 are required for activation, which is a consequence of an increased affinity for both ATP and the peptide substrate and has no effect on kcat, the intrinsic catalytic activity of the enzyme. KDR kinase catalyzes phosphotransfer by formation of a ternary complex with ATP and the peptide substrate. We demonstrate that tyrosine kinase antagonists can preferentially inhibit either the unactivated or activated form of the enzyme.

Rapid X-ray diffraction analysis of HIV-1 protease-inhibitor complexes: inhibitor exchange in single crystals of the bound enzyme.

The ability to replace an inhibitor bound to the HIV-1 protease in single crystals with other potent inhibitors offers the possibility of investigating a series of protease inhibitors rapidly and conveniently with the use of X-ray crystallography. This approach affords a fast turnaround of structural information for iterative rational drug designs and obviates the need for studying the complex structures by co-crystallization. The replacement approach has been successfully used with single crystals of the HIV-1 protease complexed with a weak inhibitor. The structures of the complexes obtained by the replacement method are similar to those determined by co-crystallization.

Synthesis, antiviral activity, and bioavailability studies of gamma-lactam derived HIV protease inhibitors.

Incorporation of a gamma-lactam in hydroxyethylene isosteres results in modest inhibitors of HIV-1 protease. Additional structural activity studies have produced significantly more potent inhibitors with the introduction of the trisubstituted cyclopentane (see compound 20) as the optimum substituent for the C-terminus. This new amino acid amide surrogate can be readily prepared in large scale from (R)-pulegone. Optimized compounds (36) and (60) are potent antiviral agents and are well absorbed (15-20%) in a dog model after oral administration.

Purchaser quality measures: progressing from wants to needs.

BACKGROUND: Purchaser demands for hospital performance data are based on the fundamental nature of benefits management-the need to reconcile costs and results. The evolution from cost-based delivery of services to prospectively priced, value-based services is occurring concurrently with the adoption of quality improvement approaches. ISSUES: The "wants" for data that purchasers articulate sometimes hide the "needs" the wants were meant to satisfy. A more efficient information agenda can be developed by exploring the nature of these needs for patients, who receive the benefits, and purchasers, who pay for them. Characteristics such as sensitivity, importance, feasibility, validity, and believability for outcome measures are discussed and then used to evaluate three popular measures of quality: cesarean section (C-section), mammography screening, and coronary artery bypass graft mortality rates. CONCLUSION: By focusing on disease/treatment/outcome-specific measurement systems, information sets helping patients, providers, and purchasers to achieve the best possible quality of outcome can be efficiently developed.

Lessons from industry.

Rapidly emerging in public debate as the key to the future of the health care industry is quality. One can hardly pick up a health care magazine or journal or listen to a discussion among health care professionals without quality becoming a concern. Despite virtually universal agreement on the importance of the generic term and secondary agreement on the importance of being able to measure it, discussion bogs down in either of two ways. It may become overwhelmed by the sheer magnitude of the task of describing all the elements of health care quality, or the different viewpoints of individuals will yield quite variable understandings of what the term "quality of health care" means. To make substantial progress in improving health care quality, we will need to come to an agreement on terms.