Characterization of bradykinin receptors in guinea pig gall bladder

Specific binding of [3H]bradykinin (BK) to guinea pig gall bladder (GPGB) membranes was protein dependent, rapid (Kon = 0.067 min-1) with high affinity (Kd = 0.45 +/- 0.02; n = 3), saturable (Bmax = 546 +/- 56 fmol/mg of protein) and showed no cooperativity (nH = 1.19 +/- 0.08). A BK B2 receptor type was indicated by the rank order of potency for inhibition of binding by B2 antagonists, [(D)Arg-[Hyp3,Thi5,(D)Tic7-Oic8]-bradykinin (HOE140) > (D)Arg-[Hyp3,(D)HypE(transpropyl)7-Oic8]-bradykinin (NPC17731) > (D)Arg-[Hyp3,Thi5, (D)Tic7-Tic8]-bradykinin (NPC16731) > (D)Arg-[Hyp3,(D)Phe7]-bradykinin (NPC567)] and agonists (BK = kallidin = Tyr(Me)8-BK > Tyr8-BK,> Hyp4-kallidin) as well as inactivity of the B1 agonist des(Arg9)-BK. Nonhydrolyzable GTP analogs (GTP-gamma-S and guanylyl-5'-imido-diphosphate) produced 80% inhibition of specific binding suggesting receptor coupling to guanine nucleotide-binding proteins. BK increased polyphosphoinositide hydrolysis in chopped GPGB in a concentration-dependent manner (0.01-300 microM; EC50 = 414 +/- 171 nM; n = 3-9 tissues/concentration). HOE140 and NPC16731, inhibited BK-induced polyphosphoinositide hydrolysis but only the latter appeared competitive (pKb 8.09 +/- 0.19, n = 3). U73122, an inhibitor of phospholipase C pathway, also inhibited BK-induced turnover in GPGB (IC50 = 46.9 +/- 17.3 nM). BK produced a concentration-related contraction of isolated strips of GPGB. Indomethacin significantly decreased both the potency and efficacy of BK whereas thiorphan, a neutral endopeptidase inhibitor, and/or captopril, an angiotensin-converting enzyme inhibitor, enhanced potency.(ABSTRACT TRUNCATED AT 250 WORDS)

Reconstitution of a nine-protein system that initiates bacteriophage lambda DNA replication

We have established an in vitro system, composed of highly purified bacteriophage lambda and Escherichia coli proteins, that specifically replicates supercoiled templates bearing the lambda replication origin (ori lambda). The complete system is composed of three groups of proteins: the virus-encoded initiator proteins (the lambda O and P proteins), the E. coli replication fork propagation machinery (single-stranded DNA-binding protein, dnaB helicase, dnaG primase, DNA polymerase III holoenzyme, and DNA gyrase), and two bacterial heat shock proteins (dnaJ and dnaK proteins). DNA replication in this system is initiated at or near ori lambda and proceeds unidirectionally rightwards through theta-structure intermediates, ultimately yielding a pair of intertwined daughter circles as the final product. In striking contrast to the situation in vivo and in crude in vitro systems, initiation of lambda DNA replication in the purified protein system does not require "transcriptional activation" of the origin region by E. coli RNA polymerase. We conclude that E. coli primase generates the primers for all leading and lagging strand DNA chains synthesized in this reconstituted lambda replication system.

Specialized nucleoprotein structures at the origin of replication of bacteriophage lambda: localized unwinding of duplex DNA by a six-protein reaction

The O protein of bacteriophage lambda localizes the initiation of DNA replication to a unique site on the lambda genome, ori lambda. By means of electron microscopy, we infer that the binding of O to ori lambda initiates a series of protein addition and transfer reactions that culminate in localized unwinding of the origin DNA, generating a prepriming structure for the initiation of DNA replication. We can define three stages of this prepriming reaction, the first two of which we have characterized previously. First, dimeric O protein binds to multiple DNA binding sites and self-associates to form a nucleoprotein structure, the O-some. Second, lambda P and host DnaB proteins interact with the O-some to generate a larger complex that includes additional DNA from an A + T-rich region adjacent to the O binding sites. Third, the addition of the DnaJ, DnaK, and Ssb proteins and ATP results in an origin-specific unwinding reaction, probably catalyzed by the helicase activity of DnaB. The unwinding reaction is unidirectional, proceeding "rightward" from the origin. The minimal DNA sequence competent for unwinding consists of two O binding sites and the adjacent A + T-rich region to the right of the binding sites. We conclude that the lambda O protein localizes and initiates a six-protein sequential reaction responsible for but preceding the precise initiation of DNA replication. Specialized nucleoprotein structures similar to the O-some may be a general feature of DNA transactions requiring extraordinary precision in localization and control.

Purification and general characterization of FAD synthetase from rat liver

Flavin adenine dinucleotide synthetase (ATP:FMN adenylyltransferase, EC 2.7.7.2) has been enriched more extensively than previously from fresh rat liver. For this, 10% homogenates in sucrose-phosphate buffer were treated with 0.1% Tween-20 prior to high-speed centrifugation to obtain soluble proteins. Those precipitated by 40% saturation with ammonium sulfate were subjected to stepwise addition of calcium phosphate gel to remove pyrophosphatase, and the remaining synthetase was further enriched by passage through a tricalcium phosphate column. An apparent yield of greater than 70% and purification over 70-fold was achieved from the high-speed supernatant fraction. The synthetase activity in solution at 4 degrees was largely lost within a week unless protected by thiols which could partly restore inactivated enzyme. The pH optimum for synthetase activity is near 7.7 when assayed with suitable concentrations of FMN, ATP, and Mg2+. Purified enzyme could be separated into lower (140,000) and higher (325,000) molecular weight components when subjected to molecular sieving on a Sephadex G-200 column.

Bovine liver mitochondrial monoamine oxidase is not an iron-dependent enzyme

It has been reported that rat liver monoamine oxidase is an iron-dependent enzyme. Calculations from reported data suggest that rat liver monoamine oxidase contains 2 g atoms of iron/mol of enzyme. However, our data over a 16-year period show that our purified bovine liver monoamine oxidase does not contain sufficient iron to justify being considered an iron protein. In order to ensure the correctness of the iron content, two microchemical analyses and atomic absorption spectroscopy were used to determine the iron content of wet ashed samples. The iron content was also determined during successive steps of enzyme purification and was found to decrease rather than increase. Monoamine oxidase, being a hydrophobic outer membrane enzyme, is very difficult to purify and detailed tests for homogeneity are necessary. Our preparations show a single band when examined by sodium dodecyl sulfate-polyacrylamide disc electrophoresis and behave as a pure protein by end group analysis. Thus, bovine liver monoamine oxidase is not an iron-dependent enzyme.

Mechanism of action of glutaryl-CoA and butyryl-CoA dehydrogenases. Purification of glutaryl-CoA dehydrogenase

Glutaryl-CoA dehydrogenase, a flavoprotein, catalyzes the reaction -OOCCH3CH2--CH2COSR (FAD leads to FADH2) leads to CH3CH = CHCOSR + CO2 (SR = CoA or pantetheine). With the isolated enzyme, a dye serves as the final electron acceptor. The enzyme from Pseudomonas fluorescens (ATCC 11250) has been purified to homogeneity. It was established with appropriate isotopic substitutions that the proton which is added to the gamma position of the product, subsequent to decarboxylation, is not derived from the solvent but is derived from the alpha position of the substrate. Under conditions where no net conversion of substrate occurs, i.e., in the absence of electron acceptor, the enzyme catalyzes the exchange of the beta hydrogen of the substrate with solvent protons. Butyryl-CoA dehydrogenase (M. elsedenii), which catalyzes an analogous reaction, catalyzes the exchange of both the alpha and beta hydrogens with solvent protons in the absence of electron acceptor. Glutaryl-CoA dehydrogenase and butyryl-CoA dehydrogenase are irreversibly inactivated by the substrate analogues 3-butynoylpantetheine and 3-pentynoylpantetheine. These inactivators do not form an adduct with the flavin and probably react with a nucleophile at the active site. Upon inactivation, the spectrum of the enzyme-bound flavin is essentially unchanged, and the flavin can be reduced by Na2S2O4. We suggest that inactivation involves intermediate allene formation. We proposed that these results support an oxidation mechanism for glutaryl-CoA dehydrogenase and butyryl-CoA dehydrogenase which is initiated by proton abstraction. With glutaryl-CoA dehydrogenase, the base, which abstracts the substrate alpha proton, is shielded from the solvent and is then used to protonate the carbanion (CH2--CH--CHCOSCoA) formed after oxidation and decarboxylation.

The reaction of sulfhydryl reagents with bovine hepatic monoamine oxidase. Evidence for the presence of two cysteine residues essential for activity

The bovine liver monoamine oxidase (EC 1.4.3.4) was found to be inactivated by various well-known sulfhydryl reagents like p-mercuribenzoate, methylmercuric iodide and 5,5'-dithiobis-(2-nitro benzoic acid). The present investigation shows that the inactivation of the enzyme results from reactions of these reagents with 2 out of 8 titratable sulfhydryl groups per 10(5) g of the enzyme. The substrate, benzylamine, and competitive inhibitors like benzaldehyde, p-nitrobenzaldehyde, benzyl alcohol protected the enzyme from inactivation by the mercurials or the Ellman reagent. The inactivation experiments with these sulfhydryl reagents, the protection experiments, and the kinetics as well as physicochemical observations suggest that there are only two cysteine residues that are required for activity of the enzyme. It is possible that these two residues may be active-center residues.

Sex bias in psychotherapy: a failure to confirm

The authors examined the questions of sex-related countertransference and bias in psychotherapy by asking 65 male and 57 female experienced group therapists for clinical reactions to case materials of a bogus outpatient who was designated either male or female. They found that varying the patient's gender produced only small differences in the therapists' responses, and conclude that sex-related countertransference problems may not be as prevalent as had been previously thought.