Reconstitution of the Ubiquinone-dependent pyruvate oxidase system of Escherichia coli with the cytochrome o terminal oxidase complex

The aerobic respiratory chain of Escherichia coli is branched and contains two terminal oxidases. The chain predominant when the cells are grown with low aeration terminates with the cytochrome d terminal oxidase complex, and the branch present under high aeration ends with the cytochrome o terminal oxidase complex. Previous work has shown that cytochrome d complex functions as a ubiquinol-8 oxidase, and that a minimal respiratory chain can be reconstituted in proteoliposomes with a flavoprotein dehydrogenase (pyruvate oxidase), ubiquinone-8, and the cytochrome d complex. This paper demonstrates that the cytochrome o complex functions as an efficient ubiquinol-8 oxidase in reconstituted proteoliposomes, and that ubiquinone-8 serves as an electron carrier from the flavoprotein to the cytochrome complex. The maximal turnover (per cytochrome o) achieved in reconstituted proteoliposomes is at least as fast as observed in E. coli membrane preparations. Electron flow from the flavoprotein to oxygen in the reconstituted proteoliposomes generates a transmembrane potential of at least 120 mV, negative inside, which is sensitive to ionophore uncouplers and inhibitors of the terminal oxidase. These data demonstrate the minimal composition of this respiratory chain as a flavoprotein dehydrogenase, ubiquinone-8, and the cytochrome o complex. Previous models have suggested that cytochrome b556, also a component of the E. coli inner membrane, is required for electron flow to cytochrome o. This is apparently not the case. It now is clear that both of the E. coli terminal oxidases act as ubiquinol-8 oxidases and, thus, ubiquinone-8 is the branch point between the two respiratory chains.

Models of the two heme centers in cytochrome oxidase. The optical properties of cytochrome a and a3

High and low spin complexes of ferric and ferrous heme a have been prepared and characterized spectroscopically. Bis(1-methylimidazole) heme a provides a good model for cytochrome a in both oxidation states while several spectral properties of cytochrome a3 can be reproduced by 1,2-dimethylimidazole heme a3. The visible absorbance spectra of these analogs account well for the absorbance spectra of oxidized and reduced cytochrome oxidase and support the conclusion (Vanneste, W. (1966) Biochemistry 5, 838-848) that cytochrome a provides the major contribution to the spectral changes in the 600 nm band upon reduction. The 655 nm band present in cytochrome oxidase appears to be a characteristic of high spin heme a+3.

Pharmacodynamic studies with (-)-3-phenoxy-N-methylmorphinan in rats

Analgesia and brain and plasma concentrations of (-)-3-phenoxy-N-methylmorphinan (PMM) and its metabolites were determined in rats administered 50 mg/kg of 3H-labeled PMM p.o., an approximate ED50. Unchanged PMM and two active metabolites, levorphanol and a different phenol, p-hydroxylated on the 3-phenoxy group (pOH-PMM), were present in brain at concentrations greater than in plasma. Analgesia was observed from 1 to 6 hr and was associated with brain concentrations of 400-1400 ng/g of PMM, 190-300 ng/g of pOH-PMM, and 16-27 ng/g of levorphanol. The presence of 58% of the administered dose as unchanged PMM in the gastrointestinal tract at 6 hr may reflect slow absorption and explain the persisting brain concentrations of PMM and its metabolites as well as the prolonged analgesia. Analgesia may have been due to the presence in brain of only PMM, pOH-PMM or levorphanol, or to the combined activity of two or three of these substances. Administration of the approximate ED50 of 3H-labeled levorphanol (0.1 mg/kg, s.c., or 6 mg/kg, p.o.) resulted in brain levorphanol concentrations (11-18 ng/g) close to those observed when PMM was administered p.o. at 50 mg/kg. After administration of an approximate subcutaneous ED50 of [3H]pOH-PMM of 24 mg/kg, the brains contained pOH-PMM (1500-4100 ng/g) and levorphanol (60-100 ng/g); these levorphanol concentrations were higher than those found after administration of the approximate ED50 of PMM or levorphanol. The findings indicate that brain levorphanol concentrations resulting from administration of PMM or pOH-PMM to rats may account for the analgesic activity observed, i.e. that PMM and pOH-PMM may act as prodrugs for levorphanol

Generic Identification of Cooked and Frozen Crabmeat by Thin Layer Polyacrylamide Gel Isoelectric Focusing: Collaborative Study

Ten collaborators were required to focus the ureaextracted proteins from 14 crabmeat samples. Six of the samples were knowns and were labeled as to their species. Eight samples were unidentified as to species and were labeled with letters. The 8 unknowns were identified by comparing the focused patterns with the patterns of the 6 species-labeled crabmeat samples. Seventy-nine samples were identified with 97.5% accuracy. This method has been adopted official first action.

The effects of temperature on human compound action potentials

The upper limbs of 10 healthy subjects were cooled and then warmed over physiological temperature ranges. The compound action potentials of median digital nerves, median sensory nerve at the wrist, radial sensory nerve at the wrist, and median thenar muscle, all showed progressive reduction in latency, amplitude, duration and area during rising temperature. Our studies suggest that the sensory compound action potential changes occur predominantly because of the summated effects of reduction in the duration of the action potentials of single myelinated fibres, although disproportionate increase in the conduction velocity of larger myelinated fibres also plays a role.

Variables influencing "lining up the shot" in golf putting

A laboratory program for the study of golf-putting skills is described. A brief description of the method and apparatus is followed by a general presentation of experimental results which helped determine the technique now in use.