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The effect of the dipole potential field of extended membrane spanning alpha-helices on the redox potentials of b cytochromes in energy transducing membranes has been calculated in the context of a three phase model for the membrane. In this model, the membrane contains three dielectric layers; (i) a 40-A hydrophobic membrane bilayer, with dielectric(More)
The ubiquitous and obligatory association of cytochrome b-559 with the photosystem II reaction center of oxygenic photosynthesis is a conundrum since it seems not to have a function in the primary electron transport pathway of oxygen evolution. A model for the cytochrome structure that satisfies the cis-positive rule for membrane protein assembly consists(More)
We have used immuno-gold labeling and electron microscopy to study the topography of thylakoid membrane polypeptides. Thylakoid vesicles formed by passage through a French press were adsorbed onto a plastic film supported by an electron microscope grid and processed for single or double immuno-gold labeling. After shadowing with platinum, the inside-out and(More)
Urinary hippuric acid (HA), of molecular weight 180 Da, is one of the major metabolites in toluene-exposed humans and is a major biological indicator. Simple and ubiquitous monitoring of exposure to toluene is very important in occupational health care, and a microfluidic chip-based electrochemical immunoassay for rapid and quantitative detection of HA in(More)
The COOH-terminal domain of the 80-residue cytochrome b559 alpha-subunit (psbE gene product) in Synechocystis sp. PCC 6803 was sequentially truncated in order to determine the minimum polypeptide length needed for function and assembly. A stop codon was introduced into the Arg-50, Arg-59, or Tyr-69 codons of the psbE gene, generating mutants truncated by(More)
Protease accessibility and antibody to a COOH-terminal peptide were used as probes for the in situ topography of the Mr 10,000 psbE gene product (alpha subunit) of the chloroplast cytochrome b-559. Exposure of thylakoid membranes to trypsin or Staphylococcus aureus V8 protease cleaved the alpha subunit to a slightly smaller polypeptide (delta Mr(More)
The topography of the heme prosthetic group of cytochrome b-559 of the photosystem II reaction center was determined from measurement of the orientation of its alpha- and beta-polypeptides in thylakoid membranes of spinach chloroplasts and in osmotically disrupted cells of the cyanobacterium Synechocystis sp. PCC 6803. The accessibility to trypsin(More)
The following findings concerning the structure of the cytochrome b6f complex and its component polypeptides, cyt b6, subunit IV and cytochrome f subunit are discussed: (1) Comparison of the amino acid sequences of 13 and 16 cytochrome b6 and subunit IV polypeptides, respectively, led to (a) reconsideration of the helix lengths and probable interface(More)
The prominent interdomain basic surface region seen in the high-resolution structure of the active lumen-side C-terminal fragment of turnip cytochrome f, containing the conserved Lys58,65,66 (large domain) and Lys187 (small domain), has been inferred from in vitro studies to be responsible for docking of its physiological oxidant, plastocyanin. The effect(More)
Toluene, a clear, colorless liquid with a distinctive smell, is the most commonly used industrial organic solvent. The adverse effects of chronic toluene exposure have been reported. The abuse of volatile substances is practiced mainly by adolescents and young adults. Chronic toluene abuse causes permanent changes in brain structure correlated with brain(More)