Observation of the FeO2 and FeIVO stretching Raman bands for dioxygen reduction intermediates of cytochrome bo isolated from Escherichia coli

AbstractReaction intermediates in dioxygen reduction by the E. coli cytochrome bo-type ubiquinol oxidase were studied by time-resolved resonance Raman spectroscopy using the artificial cardiovascular system. At 0–20 μs following photolysis of the enzyme—CO adduct in the presence of O2, we observed the FeO2 stretching Raman band at 568 cm−1 which shifted to 535 cm−1 with the 18O2 derivative. These frequencies are remarkably close to those of other oxyhemoproteins including dioxygen-bound hemoglobin and aa3-type cytochrome c oxidase. In the later time range (20–40 μs), other oxygen-isotope-sensitive Raman bands were observed at 788 and 361 cm−1. Since the 781 cm−1 band exhibited a downshift by 37 cm−1 upon 18O2 substitution, we assigned it to the FeIVO stretching mode. This band is considered to arise from the ferryl intermediate, but its appearance was much earlier than the corresponding intermediate of bovine cytochrome c oxidase (> 100 μs). The 361 cm−1 band showed the 16O/18O isotopic frequency shift of 14 cm−1 similar to the case of bovine cytochrome c oxidase reaction

Activation Process of [NiFe] Hydrogenase Elucidated by High-Resolution X-Ray Analyses: Conversion of the Ready to the Unready State

SummaryHydrogenases catalyze oxidoreduction of molecular hydrogen and have potential applications for utilizing dihydrogen as an energy source. [NiFe] hydrogenase has two different oxidized states, Ni-A (unready, exhibits a lag phase in reductive activation) and Ni-B (ready). We have succeeded in converting Ni-B to Ni-A with the use of Na2S and O2 and determining the high-resolution crystal structures of both states. Ni-B possesses a monatomic nonprotein bridging ligand at the Ni-Fe active site, whereas Ni-A has a diatomic species. The terminal atom of the bridging species of Ni-A occupies a similar position as C of the exogenous CO in the CO complex (inhibited state). The common features of the enzyme structures at the unready (Ni-A) and inhibited (CO complex) states are proposed. These findings provide useful information on the design of new systems of biomimetic dihydrogen production and fuel cell devices

Evolution of the Genus Camellia Based on the Biological Interaction and the Historical Background

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Type III Cu mutants of Myrothecium verrucaria bilirubin oxidase

金沢大学理工研究域物質化学系Type III Cu ligand, His456 and His458, of Myrothecium verrucaria (MT-1) bilirubin oxidases (BO) [EC 1.3.3.5] were doubly mutated as to Lys, Asp, and Val. In spite of perturbation of the type III Cu centers, these mutants were pale blue or colourless when isolated. However, they became intense blue on reaction with reducing agents such as dithionite, ascorbate, hexacyanoferrate(II), and octacyanotangstate(IV) under air, or with an oxidizing agent such as hexacyanoferrate(III), indicating that they are in mixed forms when expressed in Aspergillus oryzae. His456.458Lys and His456.458Asp mutated as to potential coordinating groups showed weak BO and ferroxidase activities, while His 456.458Val mutated as to non-coordinating groups showed no enzyme activity at all

Four-electron reduction of dioxygen by a multicopper oxidase, CueO, and roles of Asp112 and Glu506 located adjacent to the trinuclear copper center

金沢大学理工研究域物質化学系The mechanism of the four-electron reduction of dioxygen by a multicopper oxidase, CueO, was studied based on reactions of single and double mutants with Cys500, a type I copper ligand, and the noncoordinating Asp112 and Glu506, which form hydrogen bonds with the trinuclear copper center directly and indirectly via a water molecule. The reaction of C500S containing a vacant type I copper center produced intermediate I in an EPR-silent peroxide-bound form. The formation of intermediate I from C500S/D112N was restricted due to a reduction in the affinity of the trinuclear copper center for dioxygen. The state of intermediate I was realized to be the resting form of C500S/E506Q and C500S of the truncated mutant Δα5-7CueO, in which the 50 amino acids covering the substrate-binding site were removed. Reactions of the recombinant CueO and E506Q afforded intermediate II, a fully oxidized form different from the resting one, with a very broad EPR signal, g < 2, detectable only at cryogenic temperatures and unsaturated with high power microwaves. The lifetime of intermediate II was prolonged by the mutation at Glu506 involved in the donation of protons. The structure of intermediates I and II and the mechanism of the four-electron reduction of dioxygen driven by Asp112 and Glu506 are discussed. © 2009 by The American Society for Biochemistry and Molecular Biology, Inc

Norway spruce postglacial recolonization of Fennoscandia

Contrasting theories exist regarding how Norway spruce recolonized Fennoscandia after the last glaciation. Here, the authors provide evidences from sedimentary ancient DNA and modern population genomics to support that Norway spruce was present in southern Fennoscandia shortly after deglaciation and the early Holocene migration from the east. Contrasting theories exist regarding how Norway spruce (Picea abies) recolonized Fennoscandia after the last glaciation and both early Holocene establishments from western microrefugia and late Holocene colonization from the east have been postulated. Here, we show that Norway spruce was present in southern Fennoscandia as early as 14.7 +/- 0.1 cal. kyr BP and that the millennia-old clonal spruce trees present today in central Sweden likely arrived with an early Holocene migration from the east. Our findings are based on ancient sedimentary DNA from multiple European sites (N = 15) combined with nuclear and mitochondrial DNA analysis of ancient clonal (N = 135) and contemporary spruce forest trees (N = 129) from central Sweden. Our other findings imply that Norway spruce was present shortly after deglaciation at the margins of the Scandinavian Ice Sheet, and support previously disputed finds of pollen in southern Sweden claiming spruce establishment during the Lateglacial.Peer reviewe

Redox-dependent conformational changes of a proximal [4Fe-4S] cluster in Hyb-type [NiFe]-hydrogenase to protect the active site from O2

Citrobacter sp. S-77 [NiFe]-hydrogenase harbors a standard [4Fe–4S] cluster proximal to the Ni–Fe active site. The presence of relocatable water molecules and a flexible aspartate enables the [4Fe–4S] to display redox-dependent conformational changes. These structural features are proposed to be the key aspects that protect the active site from O2 attack

Relative Role of Flower Color and Scent on Pollinator Attraction: Experimental Tests using F1 and F2 Hybrids of Daylily and Nightlily

The daylily (Hemerocallis fulva) and nightlily (H. citrina) are typical examples of a butterfly-pollination system and a hawkmoth-pollination system, respectively. H. fulva has diurnal, reddish or orange-colored flowers and is mainly pollinated by diurnal swallowtail butterflies. H. citrina has nocturnal, yellowish flowers with a sweet fragrance and is pollinated by nocturnal hawkmoths. We evaluated the relative roles of flower color and scent on the evolutionary shift from a diurnally flowering ancestor to H. citrina. We conducted a series of experiments that mimic situations in which mutants differing in either flower color, floral scent or both appeared in a diurnally flowering population. An experimental array of 6×6 potted plants, mixed with 24 plants of H. fulva and 12 plants of either F1 or F2 hybrids, were placed in the field, and visitations of swallowtail butterflies and nocturnal hawkmoths were recorded with camcorders. Swallowtail butterflies preferentially visited reddish or orange-colored flowers and hawkmoths preferentially visited yellowish flowers. Neither swallowtail butterflies nor nocturnal hawkmoths showed significant preferences for overall scent emission. Our results suggest that mutations in flower color would be more relevant to the adaptive shift from a diurnally flowering ancestor to H. citrina than that in floral scent

Oligomerization of cytochrome c, myoglobin, and related heme proteins by 3D domain swapping

Oligomerization of heme proteins is useful for construction of new materials with cooperative and systematic functions; thus, diverse methods have been applied for construction of artificial heme protein oligomers. Three-dimensional (3D) domain swapping is a protein oligomerization phenomenon that exchanges the same domain or secondary structural element between molecules. 3D domain swapping was first reported in 1994; since then many proteins have been reported to domain swap. Our research group has been showing that various heme proteins domain swap. We also found that domain swapping of heme proteins occurs at the early stage of protein folding, and utilized it to construct various heme protein assemblies, including nanorings, cages, hetero dimers with different active sites, and a ligand-binding reversible monomer–polymer system. In this review, the basics and applications of domain swapping of heme proteins are summarized