Pseudomonas aeruginosa has two genes encoding ferredoxin NADP(+) reductases, denoted fprA and fprB. We show here that P. aeruginosa fprA is an essential gene. However, the ΔfprA mutant could only be successfully constructed in PAO1 strains containing an extra copy of fprA on a mini-Tn7 vector integrated into the chromosome or carrying it on a temperature-sensitive plasmid. The strain containing...

N A D P H , N A D P + Photoreduction, Etioplasts, Absorbance Difference Spectra, Phaseolus vulgaris It has been investigated if photoreduction of N A D P + (detected by absorption spectroscopy) may take place in lysed plastids within minutes of exposure to light. This process was made possible by removal of oxidants from the reaction mixture. Lysed plastids were suspended in a medium containing...

Giardia lamblia and Entamoeba histolytica are amitochondriate, microaerophilic protists which use fermentation enzymes like those of bacteria to survive anaerobic conditions within the intestinal lumen. Genes encoding fermentation enzymes and related electron transport peptides (e.g., ferredoxins) in giardia organisms and amebae are hypothesized to be derived from either an ancient anaerobic eu...

Cytochrome P450s (P450s) are key enzymes in the synthesis of bioactive natural products in plants. Efforts to harness these enzymes for in vitro and whole-cell production of natural products have been hampered by difficulties in expressing them heterologously in their active form, and their requirement for NADPH as a source of reducing power. We recently demonstrated targeting and insertion of ...

The currently prevalent concept of the generation of photosynthetic reducing power in oxygen-evolving cells envisions a linear (noncyclic) electron flow from water to ferredoxin (and thence to NADP(+)) that requires the collaboration of photosystems I and II (PSI and PSII) joined by plastoquinone and other electron carriers (the Z scheme). The essence of the Z scheme is that only PSI can reduce...

COMMENTARY Correction for “Mitochondrial metabolism is regulated by thioredoxin,” by Ian Max Møller, which appeared in issue 11, March 17, 2015, of Proc Natl Acad Sci USA (112:3180–3181; first published March 9, 2015; 10.1073/pnas.1502425112). The authors note that on page 3181, left column, second full paragraph, line 14, “thioredoxin reductase using NADPH” should instead appear as “ferredoxin...

Midpoint potentials of plant-type ferredoxins from a range of sources were measured by redox titrations combined with electron-paramagnetic-resonance spectroscopy. For ferredoxins from higher plants, green algae and most red algae, the midpoint potentials (at pH 8.0) were between --390 and --425 mV. Values for the major ferredoxin fractions from blue-green algae were less negative (between --32...

Productive biomolecular recognition requires exquisite control of affinity and specificity. Accordingly, nature has devised many strategies to achieve proper binding interactions. Bacterial multicomponent monooxygenases provide a fascinating example, where a diiron hydroxylase must reversibly interact with both ferredoxin and catalytic effector in order to achieve electron transfer and O2 activ...

A simple procedure for purification of ferredoxin from a green alga, Scenedesmus, is described. Crystalline ferredoxin had an absorption spectrum with maxima at 276, 330, 421, and 464 rnp and with minima at 255, 293, 390, and 445 rnp. The ratios of the optical densities at 421 and 330 rnp to that at 276 rnp were 0.651 and 0.883, respectively. The substance was shown to be pure by disc electroph...

Protein-based hydrogels usually do not exhibit high stretchability or toughness, significantly limiting the scope of their potential biomedical applications. Here we report the engineering of a chemically cross-linked, highly elastic and tough protein hydrogel using a mechanically extremely labile, de novo-designed protein that assumes the classical ferredoxin-like fold structure. Due to the lo...