Kenichi Iwata

Crystal structure of the ferredoxin component of carbazole 1,9a‐dioxygenase of Pseudomonas resinovorans strain CA10, a novel Rieske non‐heme iron oxygenase system

The carbazole 1,9a‐dioxygenase (CARDO) system of Pseudomonas resinovorans strain CA10 catalyzes the dioxygenation of carbazole; the 9aC carbon bonds to a nitrogen atom and its adjacent 1C carbon as the initial reaction in the mineralization pathway. The CARDO system is composed of ferredoxin reductase (CarAd), ferredoxin (CarAc), and terminal oxygenase (CarAa). CarAc acts as a mediator in the electron transfer from CarAd to CarAa. To understand the structural basis of the protein–protein interactions during electron transport in the CARDO system, the crystal structure of CarAc was determined at 1.9 Å resolution by molecular replacement using the structure of BphF, the biphenyl 2,3‐dioxygenase ferredoxin from Burkholderia cepacia strain LB400 as a search model. CarAc is composed of three β‐sheets, and the structure can be divided into two domains, a cluster‐binding domain and a basal domain. The Rieske [2Fe–2S] cluster is located at the tip of the cluster‐binding domain, where it is exposed to solvent. While the overall folding of CarAc and BphF is strongly conserved, the properties of their surfaces are very different from each other. The structure of the cluster‐binding domain of CarAc is more compact and protruding than that of BphF, and the distribution of electric charge on its molecular surface is very different. Such differences are thought to explain why these ferredoxins can act as electron mediators in respective electron transport chains composed of different‐featured components. Proteins 2005.

Isolation and characterization of an alkaliphilic bacterium utilizing pyrene as a carbon source.

Alkaliphilic Mycobacterium sp. strain MHP-1, which can grow on pyrene as a sole carbon and energy source, was isolated from a soil sample. At the optimum pH for growth (pH 9), about 50% of pyrene (final concentration at 0.1% [w/v]) was degraded during 7 d of incubation, and 4,5-phenanthrenedioic acid, 4-phenanthroic acid and phthalic acid were identified as metabolic intermediates. Strain MHP-1 was found to possess aromatic-ring dioxygenase genes, which are highly homologous to the known nidAB genes from pyrene-degrading mycobacteria.

Expression, purification, and characterization of 2′-aminobiphenyl-2, 3-diol 1,2-dioxygenase from carbazole-degrader Pseudomonas resinovorans strain CA10

The two-subunit meta-cleavage enzyme, 2′-aminobiphenyl-2,3-diol 1,2-dioxygenase (CarBaBb), from the carbazole degrader Pseudomonas resinovorans strain CA10 was purified to homogeneity from an Escherichia coli strain carrying the expression vector pUCA503, in which two copies of the carBaBb genes are tandemly linked. SDS-PAGE and gel filtration showed that CarB was a α2β2-heterotetrameric enzyme with subunit molecular masses of approximately 10,000 for CarBa and 29,000 for CarBb. The optimum pH for activity was 8.5 and that of temperature was 35°C. The CarB enzyme had a K m of 14 μM and a k cat/K m of 0.25 μM−1 s−1 for 2′-aminobiphenyl-2,3-diol, and the catalytic activities for biphenyl-type catecholic substrates were higher than those for monoaromatic catechol derivatives. The enzyme was originally isolated as a meta-cleavage enzyme for 2′-aminobiphenyl-2,3-diol involved in carbazole degradation, but the enzyme was highly specific for 2,3-dihydroxybiphenyl.

Purification and Characterization of meta-Cleavage Compound Hydrolase from a Carbazole Degrader Pseudomonas resinovorans Strain CA10

2-Hydroxy-6-oxo-6-(2′-aminophenyl)-hexa-2,4- dienoic acid [6-(2′-aminophenyl)-HODA] hydrolase, involved in carbazole degradation by Pseudomonas resinovorans strain CA10, was purified to near homogeneity from an overexpressing Escherichia coli strain. The enzyme was dimeric, and its optimum pH was 7.0-7.5. Phylogenetic analysis showed the close relationship of this enzyme to other hydrolases involved in the degradation of monocyclic aromatic compounds, and this enzyme was specific for 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoic acid (6-phenyl-HODA), having little activity toward 2-hydroxy-6-oxohepta-2,4-dienoic acid and 2-hydroxymuconic semialdehyde. The enzyme had a Km of 2.51 μM and kcat of 2.14 (s−1) for 6-phenyl-HODA (50 mM sodium phosphate, pH 7.5, 25°C). The effect of the presence of an amino group or hydroxyl group at the 2′-position of phenyl moiety of 6-phenyl-HODA on the enzyme activity was found to be small; the activity decreased only in the order of 6-(2′-aminophenyl)-HODA (2.44 U/mg)>6-phenyl-HODA (1.99 U/mg)>2-hydroxy-6-oxo-6-(2′-hydroxyphenyl)-hexa-2,4-dienoic acid (1.05 U/mg). The effects of 2′-substitution on the activity were in accordance with the predicted reactivity based on the calculated lowest unoccupied molecular orbital energy for these substrates.

4.4 A 197mW 70ms-latency full-HD 12-channel video-processing SoC for car information systems

Todays car information systems (CIS) are growing into integrated cockpit systems, supporting not solely infotainment, such as navigation and AV playing/recording, but also driver assistance, such as surround view systems. Also, in-car video transfer via Ethernet is becoming widespread. Such networks connect camera modules, head unit controllers and rear-seat display units, and carry video signals encoded in H.264 according to EthernetAVB. Thus, it is necessary for integrated cockpit systems to handle significant amounts of video processing. A key requirement for such systems is also low power consumption and thermal management for stable operation.

Intra texture prediction based on repetitive pixel replenishment

A new intra prediction scheme based on intra repetitive pixel replenishment is proposed. This scheme improves intra coding efficiency by generating adaptive texture according to an intra displacement vector that reduces prediction error for cyclic patterns and differential motion vector coding. Simulation results showed that the proposed technique improved coding efficiency by up to 2.5% BD-Rate (ΔBitrate in [%]) compared with version 3.0 of common software for High Efficiency Video Coding; encoding time was increased by 20%. The total improvement in intra coding efficiency with respect to existing H.264/AVC intra prediction was 5.0% on average and with a maximum of 10.3%. Because the proposed scheme did not need to estimate the decoder-side motion, there was no significant increase in decoding time.

Ammonia Accumulation of Novel Nitrogen-Fixing Bacteria

Nitrogen is an essential element for many biological processes, including those occurring in plants (Ogura et al., 2006). Despite the abundance of atmospheric nitrogen, production of nitrogen fertilisers by the Harber–Bosch process is increasing annually due to the deficiency of ammonia produced by biological nitrogen fixation—the enzyme-catalyzed reduction of nitrogen gas (N2). Concern over ‘greenhouse’ gasses emitted by the Harber–Bosch process has resulted in a research focus on nitrogen-fixing bacteria, and in particular, their genetic modification to excrete excess ammonia for agricultural purposes (Terzaghi, 1980; Saikia & Jain, 2007).

Crystallization and preliminary crystallographic analysis of the 2′-aminobiphenyl-2,3-diol 1,2-dioxygenase from the carbazole-degrader Pseudomonas resinovorans strain CA10

CarBaBb, the class III extradiol dioxygenase involved in carbazole degradation by Pseudomonas resinovorans CA10, was crystallized at 278 K by the hanging-drop vapour-diffusion method using PEG MME 550 as a precipitant. The crystals had a transparent thin square-pillar shape and belonged to space group P2(1)2(1)2, with unit-cell parameters a = 122.8, b = 144.6, c = 49.2 A, alpha = beta = gamma = 90 degrees . The crystals diffracted to a maximum resolution of 1.9 A and gave a data set with an overall R(merge) of 5.7% and a completeness of 98.6%. The V(M) value was 2.52 A(3) Da(-1), which indicated a solvent content of 51.2%.

Motion estimation using multiple image sensors

A scheme of motion estimation using multiple image sensors is proposed, in which the multiple image sensors work at different integration intervals or different sampling instances. Because combined use of multiple image sensors virtually increases the temporal resolution while keeping signal to noise ratio high enough, the accuracy of the estimation can be improved. Both gradient-based and block-matching-based methods are formulated for the images obtained by the multiple image sensors. Tile experimental results show that the proposed scheme significantly improves the accuracy and reduces computational complexity.<<ETX>>

71% Reducing the memory bandwidth requirement for a multi-standard video codec by lossless compression of video using a combination of 2D-DPCM and Variable Length Coding

Memory bandwidth is a critical issue tor a high performance and high resolution video codec. We propose a lossless compression solution to reduce memory bandwidth requirement for a multi-standard video codec. The solution is a combination of 2D-DPCM, Variable Length Coding and 4-way set-associative cache. Experimental results show that the proposed solution can reduce the memory bandwidth requirement with 71% for reference data.