Nucleotide-binding domains of cystic fibrosis transmembrane conductance regulator, an ABC transporter, catalyze adenylate kinase activity but not ATP hydrolysis.

The cystic fibrosis transmembrane conductance regulator (CFTR) is an anion channel in the ATP-binding cassette (ABC) transporter family. CFTR consists of two transmembrane domains, two nucleotide-binding domains (NBD1 and NBD2), and a regulatory domain. Previous biochemical reports suggest NBD1 is a site of stable nucleotide interaction with low ATPase activity, whereas NBD2 is the site of active ATP hydrolysis.

The structural basis for autoinhibition of FLT3 by the juxtamembrane domain.

FLT3 is a type III receptor tyrosine kinase that is thought to play a key role in hematopoiesis. Certain classes of FLT3 mutations cause constitutively activated forms of the receptor that are found in significant numbers of patients with acute myelogenous leukemia (AML). The mutations occur either in the activation loop, for example, as point mutations of Asp835 or as internal tandem duplication (ITD) sequences in the juxtamembrane (JM) domain.

Trypanocidal bisbenzylisoquinoline alkaloids are inhibitors of trypanothione reductase.

Eleven bisbenzylisoquinoline (BBIQ) alkaloids were studied for in vitro trypanocidal activity against trypomastigote forms of the Y strain of Trypanosoma cruzi. The inhibitory activity of these compounds against trypanothione reductase (TR), a target enzyme for chemotherapy against Chagas disease, was also studied. Six BBIQ alkaloids (antioquine, cepharanthine, daphnoline, limacine, cycleanine and (-) curine) displayed a 50% lethal concentration (LC50) against T.

Insulin antagonism: a novel role for human serum transferrin.

We have purified alpha2-glycoprotein (alpha2-GP), an insulin antagonist from human plasma which is induced by growth hormone (GH), and shown that pure alpha2-GP is a potent antagonist of severe insulin-induced hypoglycemia, producing acute hyperglycemia in intact rats and ketonuria in diabetic rats. The N-terminal amino acid sequence of alpha2-GP and the reactivity of alpha2-GP with an antitransferrin monoclonal antibody show that alpha2-GP is identical to human serum transferrin. Furthermore, pure human serum transferrin and non-glycosylated recombinant human transferrin reproduce the insulin antagonist effects of alpha2-GP in rats, whereas ovotransferrin shows no such effect.

Backbone makes a significant contribution to the electrostatics of alpha/beta-barrel proteins.

The electrostatic properties of seven alpha/beta-barrel enzymes selected from different evolutionary families were studied: triose phosphate isomerase, fructose-1,6-bisphosphate aldolase, pyruvate kinase, mandelate racemase, trimethylamine dehydrogenase, glycolate oxidase, and narbonin, a protein without any known enzymatic activity. The backbone of the alpha/beta-barrel has a distinct electrostatic field pattern, which is dipolar along the barrel axis. When the side chains are included in the calculations the general effect is to modulate the electrostatic pattern so that the electrostatic field is generally enhanced and is focused into a specific area near the active site.

Charge is the major discriminating factor for glutathione reductase versus trypanothione reductase inhibitors.

Benson et al. (Biochem. J.

Site-directed mutants designed to test back-door hypotheses of acetylcholinesterase function.

The location of the active site of the rapid enzyme, acetylcholinesterase, near the bottom of a deep and narrow gorge indicates that alternative routes may exist for traffic of substrate, products or solute into and out of the gorge. Molecular dynamics suggest the existence of a shutter-like back door near Trp84, a key- residue in the binding site for acetylcholine, in the Torpedo californica enzyme. The homology of the omega loop, bearing Trp84, with the lid which sequesters the substrate in neutral lipases displaying structural homology with acetylcholinesterase, suggests a flap-like back door.

Kukoamine A and other hydrophobic acylpolyamines: potent and selective inhibitors of Crithidia fasciculata trypanothione reductase.

The enzyme trypanothione reductase (TR), together with its substrate, the glutathione-spermidine conjugate trypanothione, plays an essential role in protecting parasitic trypanosomatids against oxidative stress and is a target for drug design. Here we show that a naturally occurring spermine derivative, the antihypertensive agent kukoamine A [N1N12-bis(dihydrocaffeoyl)-spermine] inhibits TR as a mixed inhibitor (Ki = 1.8 microM, Kii = 13 microM).

Consensus preferred hydration sites in six FKBP12-drug complexes.

A set of consensus hydration sites for the FK506-FKBP12 complex are derived by comparing six FKBP12-drug complexes. These hydration sites include a subset of the observed water molecules plus some sites that are occupied by neighboring protein atoms in the FK506-FKBP12 crystal structure. Two hydration prediction algorithms, AUTO-SOL and AQUARIUS2, showed significant increases in apparent efficacy using these consensus water sites, suggesting that our proposed set of consensus hydration sites is truly a better representation of the hydration properties of FKBP12 in solution.

Open "back door" in a molecular dynamics simulation of acetylcholinesterase.

The enzyme acetylcholinesterase generates a strong electrostatic field that can attract the cationic substrate acetylcholine to the active site. However, the long and narrow active site gorge seems inconsistent with the enzyme's high catalytic rate. A molecular dynamics simulation of acetylcholinesterase in water reveals the transient opening of a short channel, large enough to pass a water molecule, through a thin wall of the active site near tryptophan-84.

An electrostatic mechanism for substrate guidance down the aromatic gorge of acetylcholinesterase.

Electrostatic calculations based on the recently solved crystal structure of acetylcholinesterase (acetylcholine acetylhydrolase, EC 3.1.1.

Conformational analysis of a 12-residue analogue of mastoparan and of mastoparan X.

We have investigated the conformational properties of a truncated analogue of mastoparan and of mastoparan X, both peptides from wasp venom. The electrostatically driven Monte Carlo method was used to explore the conformational space of these short peptides. The initial conformations used in this study, mainly random ones, led to alpha-helical conformations.

Cooperativity of papain-substrate interaction energies in the S2 to S2' subsites.

Enzyme-substrate contacts in the hydrolysis of ester substrates by the cysteine protease papain were investigated by systematically altering backbone hydrogen-bonding and side-chain hydrophobic contacts in the substrate and determining each substrate's kinetic constants. The observed specificity energies [defined as delta delta G obs = -RT ln [(kcat/KM)first/(kcat/KM)second)]] of the substrate backbone hydrogen bonds were -2.7 kcal/mol for the P2 NH and -2.