Cytochrome c 6-like protein as a putative donor of electrons to photosystem I in the cyanobacterium Nostoc sp. PCC 7119

Most organisms performing oxygenic photosynthesis contain either cytochrome c 6 or plastocyanin, or both, to transfer electrons from cytochrome b 6-f to photosystem I. Even though plastocyanin has superseded cytochrome c 6 along evolution, plants contain a modified cytochrome c 6, the so called cytochrome c 6A, whose function still remains unknown. In this article, we describe a second cytochrome c 6 (the so called cytochrome c 6-like protein), which is found in some cyanobacteria but is phylogenetically more related to plant cytochrome c 6A than to cyanobacterial cytochrome c 6. In this article, we conclude that the cytochrome c 6-like protein is a putative electron donor to photosystem I, but does play a role different to that of cytochrome c 6 and plastocyanin as it cannot accept electrons from cytochrome f. The existence of this third electron donor to PSI could explain why some cyanobacteria are able to grow photoautotrophically in the absence of both cytochrome c 6 and plastocyanin. In any way, the Cyt c 6-like protein from Nostoc sp. PCC 7119 would be potentially utilized for the biohydrogen production, using cell-free photosystem I catalytic nanoparticles.Dirección General de Investigación Científica y Técnica BFU2006-01361/BMCJunta de Andalucía PAI BIO022 BIO19

Functional and Biogenetical Heterogeneity of the Inner Membrane of Rat-Liver Mitochondria

Rat liver mitochondria were fragmented by a combined technique of swelling, shrinking, and sonication. Fragments of inner membrane were separated by density gradient centrifugation. They differed in several respects: electronmicroscopic appearance, phospholipid and cytochrome contents, electrophoretic behaviour of proteins and enzymatic activities. Three types of inner membrane fractions were isolated. The first type is characterized by a high activity of metal chelatase, low activities of succinate-cytochrome c reductase and of glycerolphosphate dehydrogenase, as well as by a high phospholipid content and low contents of cytochromes aa3 and b. The second type displays maximal activities of glycerolphosphate dehydrogenase and metal chelatase, but contains relatively little cytochromes and has low succinate-cytochrome c reductase activity. The third type exhibits highest succinate-cytochrome c reductase activity, a high metal chelatase activity and highest cytochrome contents. However, this fraction was low in both glycerolphosphate dehydrogenase activity and phospholipid content. This fraction was also richest in the following enzyme activities: cytochrome oxidase, oligomycin-sensitive ATPase, proline oxidase, 3-hydroxybutyrate dehydrogenase and rotenone-sensitive NADH-cytochrome c reductase. Amino acid incorporation in vitro and in vivo in the presence of cycloheximide occurs predominantly into inner membrane fractions from the second type. These data suggest that the inner membrane is composed of differently organized parts, and that polypeptides synthesized by mitochondrial ribosomes are integrated into specific parts of the inner membrane

Systematics of Beringian threespine sticklebacks

Thesis (M.S.) University of Alaska Fairbanks, 2000In Pleistocene Beringia, large-scale glaciations exposed high latitude species to variable environmental conditions that created disjunct populations of terrestrial and marine species. The general nature of the dynamic biogeographic history of Beringia can be assessed by studying genetic patterns across many Beringian organisms. Mitochondrial DNA sequences were used to study the phylogenetic and phylogeographic structure of the threespine stickleback, Gasterosteus aculeatus. A 714 bp fragment of the cytochrome b gene was sequenced from 66 individuals from 17 locations extending from southeast Alaska northwest to coastal Siberia. These data were combined with 36 homologous cyt-b sequences from a previous study to provide a preliminary assessment of patterns of genetic variation in threespine stickleback- with a particular emphasis on Alaskan populations. Cytochrome b data show the existence of two major clades in the Pacific, with an extensive zone of overlap that spans the Bering Straits

Cytochrome c: Surfing Off of the Mitochondrial Membrane on the Tops of Complexes III and IV

The proper arrangement of protein components within the respiratory electron transport chain is nowadays a matter of intense debate, since altering it leads to cell aging and other related pathologies. Here, we discuss three current views-the so-called solid, fluid and plasticity models-which describe the organization of the main membrane-embedded mitochondrial protein complexes and the key elements that regulate and/or facilitate supercomplex assembly. The soluble electron carrier cytochrome c has recently emerged as an essential factor in the assembly and function of respiratory supercomplexes. In fact, a 'restricted diffusion pathway' mechanism for electron transfer between complexes III and IV has been proposed based on the secondary, distal binding sites for cytochrome c at its two membrane partners recently discovered. This channeling pathway facilitates the surfing of cytochrome c on both respiratory complexes, thereby tuning the efficiency of oxidative phosphorylation and diminishing the production of reactive oxygen species. The well-documented post-translational modifications of cytochrome c could further contribute to the rapid adjustment of electron flow in response to changing cellular conditions.Spanish Ministry of Economy and Competitiveness (BFU2015-71017/BMC MINECO/FEDER and PGC2018-096049-B-I00 BIO/BMC MICINN/FEDER, EU

Could CuB be the site of redox linkage in cytochrome c oxidase?

This paper explores the proton pumping function of cytochrome c oxidase [ferrocytochrome-c:oxygen oxidoreductase (EC 1.9.3.1)] based upon redox linkage at the "high-potential" CU(B) center. A model is proposed that is derived from a redox-linked ligand exchange mechanism previously described for the Cu(A) site. Qualitative analysis of this mechanism indicates that such a mechanism is feasible. However, the relatively short distance between Cu(B) and cytochrome a3 implies that the uncoupling electron transfers are quite facile. In addition, the position of the Cu(B) center with respect to the inner mitochondrial membrane argues against redox linkage at the Cu(B) site

Studies on Regioselective Binding Mode of Steroid Molecules in Homology Modeled Cytochrome P450-2C11

In this study, we investigated the regioselective binding mode of steroid molecules and structure requirements for steroid molecules for 16[alpha]-hydroxylation by Cytochrome P450-2C11. Docking study by using the homology Cytochrome P450-2C11 indicated that 16[alpha]-hydroxylation is favored with steroidal molecules possessing the following components, 1) a bent A-B ring configuration (5[beta]-reduced), 2) C-3[alpha]-hydroxyl group, 3) C-17[beta]-acetyl group, and 4) methyl group at both the C-18 and C-19. These respective steroid components requirements such as A-B ring configuration and functional groups at C-3 and C-17 were defined as the inhibitory contribution factor. Overall results by rat CYP2C11 revealed that steroidal structure requirements resulted in causing an effective inhibition of [^3^H]progesterone 16[alpha]-hydroxylation by the adult male rat liver microsome. As far as docking of homology modeled CYP2C11 against investigated steroids is concerned, they are docked at the active site superimposed with flurbiprofen. It was also found that the distance between heme iron and C16[alpha]-H was between 4 to 6 Å and that the related angle was in the range of 180±45°

Rapid identification of European (Anguilla anguilla) and North American eel (Anguilla rostrata) by polymerase chain reaction.

A rapid and cost effective DNA test is described to identify European eel (Anguilla anguilla) and North American eel (Anguilla rostrata). By means of polymerase chain reaction (PCR) technique parts of the mitochondrial cytochrome b gene are amplified with species specific primers which are designed to produce PCR fragments of different characteristic sizes for European and American eel. The size differences can easily be made visible by agarose gel electrophoresi

First molecular data of the Borneo Banteng Bos Javanicus lowi from Sabah, Borneo

Phylogenetic relationships among three subspecies of banteng, Burma banteng Bos javanicus birmanicus in mainland Southeast Asia, Javan banteng Bos javanicus javanicus in Java, and Bornean banteng Bos javanicus lowi in Borneo, and the presence/absence of interbreeding between wild Bornean banteng and domestic cattle in Sabah, Malaysia, were investigated by partial sequences of cytochrome b and D-loop of mitochondrial DNA. The results show that genetic distance of the Bornean banteng are relatively close to the gaur Bos gaurus/gayal Bos frontalis (the cytochrome b, 0.004–0.025; the D-loop, 0.012–0.021) followed by Burma banteng (the cytochrome b, 0.027–0.035; the D-loop, 0.040–0.045), and kouprey Bos sauveli (the cytochrome b, 0.031–0.035; the D-loop, 0.037–0.042). There are much greater distances between Bornean banteng and domestic cattle, Bos taurus and Bos indicus (the cytochrome b, 0.059–0.076; the D-loop, 0.081–0.090). These results suggest that the Bornean banteng diverged genetically from other banteng subspecies and that the wild Bornean banteng from this study are pure strain and have high conservation value

Variasi Gen Mitokondria Cytochrome B Pada Dua Jenis Burung Kakatua Putih (Cacatua Alba Dan C. Moluccensis)

Variation in The Mitochondrial Cytochrome b Gene in The Two White Cockatoo Species (Cacatua alba and C. molucensis). DNA sequence variation in the 791-bp of mitochondrial cytocrome b gene in the two white cockatoo species (C. alba and C. moluccensis) were analyzed in this study. Two pairs of internal primers used to amplify two fragments of cytochrome b from 30 individuals cockatoo. The results show that there were genetic variations among individuals of C. alba and C. moluccensis. Twenthy eight haplotypes occured in 30 individuals studied; 14 haplotypes (Hca1-Hca14) in 16 individuals of C. alba, and 14 haplotypes (Hcm1-Hcm14)in 14 individuals of C. moluccensis. Hca5 was dominant and owned by 3individuals (H37, KBS62, 28, BBP88). Within C. alba there were 18 variable sites, 0.00701 of nucleotide diversity (Pi), 0.975 ± 0.035 of haplotype diversity (Hd), and 0.005 ± 0.002 of mean genetic distance. Whitin C. moluccensis there were 18 variable sites, 0.00830 of Pi, and 0.9999± 0.028 of Hd, and 0,010 ± 0.002 (0.001-0.010) mean genetic distance. Divergence between C. alba and C. moluccensis was 0.064 ± 0.088 %. Neigbor-joining (NJ) analysis showed two main clusters consisted of : C. alba and C. moluccensis separately, and indicated that althoughthere were some variations in the DNA sequences, but the individuals within a species remain clustered in the same cluster

Q-band electron nuclear double resonance (ENDOR) and X-band EPR of the sulfobetaine 12 heat-treated cytochrome c oxidase complex

Heat treatment of the bovine cytochrome c oxidase complex in the zwitterionic detergent sulfobetaine 12 (SB-12) results in loss of subunit III and the appearance of a type II copper center as characterized by electron paramagnetic resonance (EPR) spectroscopy. Previous authors (Nilsson, T., Copeland, R. A., Smith, P. A., and Chan, S. I. (1988) Biochemistry 27, 8254-8260) have interpreted this type II copper center as a modified version of the CuA site. By using electron nuclear double resonance spectroscopy, it is found that the CuA proton and nitrogen resonances remain present in the SB-12 heat-treated enzyme and that three new nitrogen resonances appear having hyperfine coupling constants consistent with histidine ligation. These hyperfine coupling constants correlate well with those recently found for the CuB histidines from the cytochrome aa3-600 quinol oxidase from Bacillus subtilis (Fann, Y. C., Ahmed, I., Blackburn, N. J., Boswell, J. S., Verkhovskaya, M. L., Hoffman, B. M., and Wikström, M. (1995) Biochemistry 34, 10245-10255). In addition, the total EPR-detectable copper concentration per enzyme molecule approximately doubles upon SB-12 heat treatment. Finally, the observed type II copper EPR spectrum is virtually indistinguishable from the EPR spectrum of CuB of the as-isolated cytochrome bo3 complex from Escherichia coli. These data indicate that the type II copper species that appears results from a breaking of the strong antiferromagnetic coupling of the heme a3-CuB binuclear center