Rationale: Nitric oxide, the classic endothelium-derived relaxing factor (EDRF), acts through cyclic GMP and calcium without notably affecting membrane potential. A major component of EDRF activity derives from hyperpolarization is termed hyperpolarizing (EDHF). Hydrogen sulfide (H 2 S) a prominent EDRF, since mice lacking its biosynthetic enzyme, cystathionine γ-lyase (CSE), display pronounced hypertension with deficient vasorelaxant responses to acetylcholine. Objective: The purpose this...

PIK3CA, one of the two most frequently mutated oncogenes in human tumors, codes for p110alpha, catalytic subunit a phosphatidylinositol 3-kinase, isoform alpha (PI3Kalpha, p110alpha/p85). Here, we report 3.0 angstrom resolution structure complex between p110alpha and polypeptide containing p110alpha-binding domains p85alpha, protein required its enzymatic activity. The shows that many mutations occur at residues lying interfaces p85alpha or kinase domain other within subunit. Disruptions...

In mammals, the hydroperoxidation of arachidonic acid by lipoxygenases leads to formation leukotrienes and lipoxins, compounds that mediate inflammatory responses. Lipoxygenases are dioxygenases contain a nonheme iron present in many animal cells. Soybean lipoxygenase-1 is single-chain, 839-residue protein closely related mammalian lipoxygenases. The structure soybean solved 2.6 angstrom resolution shows enzyme has two domains: 146-residue β barrel 693-residue helical bundle. atom center...

Copper active sites play a major role in enzymatic activation of dioxygen. We trapped the copper-dioxygen complex enzyme peptidylglycine-alphahydroxylating monooxygenase (PHM) by freezing protein crystals that had been soaked with slow substrate and ascorbate presence oxygen. The x-ray crystal structure this precatalytic complex, determined to 1.85-angstrom resolution, shows oxygen binds one coppers an end-on geometry. Given structure, it is likely dioxygen directly involved electron...

The structure of the Fab′ fragment a human myeloma immunoglobulin was determined by x-ray crystallographic analysis at 2.8-Å resolution. Fourier map electron density correlated with aminoacid sequence to obtain three-dimensional model. Four globular subunits, which correspond homology regions light and heavy chains, are arranged in tetrahedral configuration. These subunits closely resemble each other, sharing basic pattern polypeptide chain folding. In subunit, long sequences tightly packed,...

Mutations in oncogenes often promote tumorigenesis by changing the conformation of encoded proteins, thereby altering enzymatic activity. The PIK3CA oncogene, which encodes p110alpha, catalytic subunit phosphatidylinositol 3-kinase alpha (PI3Kalpha), is one two most frequently mutated human cancers. We report structure common mutant p110alpha complex with interacting domains its regulatory partner (p85alpha), both free and bound to an inhibitor (wortmannin). N-terminal SH2 (nSH2) domain...

The pathology of Huntington's disease is characterized by neuronal degeneration and inclusions containing N-terminal fragments mutant huntingtin (htt). To study htt aggregation, we examined purified in vitro, finding globular protofibrillar intermediates participating the genesis mature fibrils. These were high β-structure. Furthermore, Congo Red, a dye that stains amyloid fibrils, prevented assembly into but not formation protofibrils. Other proteins capable forming ordered aggregates, such...

Many neuropeptides and peptide hormones require amidation at the carboxyl terminus for activity. Peptidylglycine α-amidating monooxygenase (PAM) catalyzes of these diverse physiological regulators. The amino-terminal domain bifunctional PAM protein is a peptidylglycine α-hydroxylating (PHM) with two coppers that cycle through cupric cuprous oxidation states. anomalous signal endogenous was used to determine structure catalytic core oxidized rat PHM without bound substrate. These structures...

Quinone reductase [NAD(P)H:(quinone acceptor) oxidoreductase, EC 1.6.99.2], also called DT diaphorase, is a homodimeric FAD-containing enzyme that catalyzes obligatory NAD(P)H-dependent two-electron reductions of quinones and protects cells against the toxic neoplastic effects free radicals reactive oxygen species arising from one-electron reductions. These participate in reductive bioactivation cancer chemotherapeutic agents such as mitomycin C tumor cells. Thus, surprisingly, same...

IgG New binds ligands such as orceine, menadione, and uridine with a low affinity (K(0) about 1 x 10(3) liter/mol) gamma-hydroxy derivative of vitamin K(1) higher = 1.7 10(5) liter/mol). Binding studies indicate that both the 2-methylnaphthoquinone rings phytyl tail hapten contribute to total binding energy. The these in crystalline state has been investigated by difference Fourier maps Fab' New-ligand complexes at 6-A resolution. A 3.5-A resolution map obtained for K(1)-Fab' complex shows...

Abstract Theoretical estimations of changes in side chain configurational entropy are essential for understanding the different contributions to overall thermodynamic behavior important biological processes like folding and binding. The any given particular protein can be evaluated from complete energy profile chain. Calculations profiles performed using single bond dihedrals as only independent variables long structures at each value allowed relax through small valence angles. probabilities...

The magnitude of the conformational entropy change experienced by peptide backbone upon protein folding was investigated experimentally and computational analysis. Experimentally, two different pairs mutants a 33 amino acid corresponding to leucine zipper region GCN4 were used for high-sensitivity microcalorimetric Each pair differed only having alanine or glycine at specific solvent-exposed position under conditions in which differences stability could be attributed unfolded state. studied...

The structural analysis of the Fab' fragment human myeloma immunoglobulin IgGl(lambda) New has been extended to a nominal resolution 2.0 A. Each subunits corresponding variable and constant homology regions light heavy chains contains two irregular beta-sheets which are roughly parallel each other surround tightly packed interior hydrophobic side chains. About 50-60% amino-acid residues included in beta-pleated sheets. Sequence alignments between obtained by comparison their...

During mitochondrial ATP synthesis, F 1 -ATPase—the portion of the synthase that contains catalytic and regulatory nucleotide binding sites—undergoes a series concerted conformational changes couple proton translocation to synthesis high levels required for cellular function. In structure rat liver -ATPase, determined 2.8-Å resolution in presence physiological concentrations nucleotides, all three β subunits contain bound adopt similar conformations. This provides missing configuration...

A common strategy to improve the potency of drug candidates is introduce chemical functionalities, like hydrogen bond donors or acceptors, at positions where they are able establish strong interactions with target. However, it often observed that added functionalities do not necessarily even if form bonds. Here, we explore thermodynamic and structural basis for those observations. KNI‐10033 a potent experimental HIV‐1 protease inhibitor picomolar affinity against wild‐type enzyme ( K d = 13...

Abstract The loss of translational degrees freedom makes an important, unfavorable contribution to the free energy binding. Examination experimental values suggest that calculation this entropy using Sackur–Tetrode equation produces largely overestimated values. Better agreement is obtained cratic entropy. Theoretical considerations volumes available for movement a ligand in solution and complex are rather similar, suggesting also provides best estimate © 1994 John Wiley & Sons, Inc.