Characterisation of the genetically modified cytochrome systems and their application to biohydrogen production in rhodobacter capsulatus

Download

index.pdf

Date

2005

Author

Öztürk, Yavuz

Metadata

Show full item record

Item Usage Stats

183
views

86
downloads

Facultative phototrophic bacterium Rhodobacter capsulatus has two c-type electron carrier cytochromes (cyt); the soluble cyt c2 and the membrane-attached cyt cy, that act as electron carriers during respiratory and photosynthetic growth of this species. Previously, a soluble form of cyt cy was constructed by fusing genetically the signal sequence of cyt c2 to the cyt c domain of cyt cy. The obtained novel soluble cyt cy (cyt S-cy) was unable to support photosynthetic growth of R. capsulatus but yielded photosynthetically functional (Ps+) revertants frequently. In the first part of this study, photosynthetic electron transfer properties of some of Ps+ revertants of cyt S-cy were analyzed by biochemical and biophysical methods and compared with the cyt cy and cyt c2. Reduction-oxidation titration of membrane supernatants showed that the redox midpoint potential of cyt S-cy was +338 mV which is similar to midpoint potentials of cyt cy or the cyt c2. However, light-activated, time resolved spectroscopy revealed that reaction center mediated oxidation kinetics of cyt S-cy exhibited only a slow phase, unlike cyt c2 which has both fast and slow phases. It therefore appeared that during electron transfer cyt S-cy does not interact with the reaction centre as tightly as cyt c2. These findings imply that attaching electron carrier cyts to the membrane allowed them to weaken their interactions with their partners, while restricting their spatial diffusion, so that they accomplish rapid multiple turnovers. In the second part of this study, hydrogen production of various R. capsulatus strains harboring the genetically modified electron carrier cytochromes, cyt cbb3 deleted and Qox deleted strains were compared with the wild type. Under photoheterotrophic growth conditions with limiting nitrogen source, the excess reducing equivalents generated by organic acid oxidation are

Subject Keywords

Genetics.

URI

http://etd.lib.metu.edu.tr/upload/3/12606961/index.pdf
https://hdl.handle.net/11511/15807

Collections

Graduate School of Natural and Applied Sciences, Thesis

Suggestions

OpenMETU
Core

Deletion mutation of GLNB and GLNK genes in rhodobacter capsulatus to enhance biohydrogen production Pekgöz, Gülşah; Gündüz, Ufuk; Eroğlu, İnci; Department of Biotechnology (2010) Rhodobacter capsulatus is a photosynthetic, purple non-sulfur (PNS) bacterium that produces biohydrogen via photofermentation. Nitrogenase enzyme is responsible for hydrogen production; during fixation of molecular nitrogen into ammonium, hydrogen is produced. Since this process is an energetically expensive process for the cell, hydrogen production is strictly controlled at different levels. When ammonium is present in the environment, hydrogen production completely ceases. The key proteins in the regulati...
Live-cell imaging of Pol II promoter activity to monitor gene expression with RNA IMAGEtag reporters SHIN, Ilchung; RAY, Judhajeet; Gupta, Vinayak; İlgü, Müslüm; Beasley, Jonathan; BENDICKSON, Lee; MEHANOVIC, Samir; Kraus, George A.; Nilsen-Hamilton, Marit (Oxford University Press (OUP), 2014-01-01) We describe a ribonucleic acid (RNA) reporter system for live-cell imaging of gene expression to detect changes in polymerase II activity on individual promoters in individual cells. The reporters use strings of RNA aptamers that constitute IMAGEtags (Intracellular MultiAptamer GEnetic tags) that can be expressed from a promoter of choice. For imaging, the cells are incubated with their ligands that are separately conjugated with one of the FRET pair, Cy3 and Cy5. The IMAGEtags were expressed in yeast from ...
Cloning and expression of periplasmic (clp p-like) and membrane-bound serine protease genes of thermoplasma volcanium in escherichia coli Demirok, Burçak; Kocabıyık, Semra; Department of Biology (2006) Serine proteases are a family of proteases that utilize an activated serine residue in the substrate-binding pocket to catalytically hydrolyze peptide bonds. Enzymes which belong to this family, with a diverse array of metabolic and regulatory functions, play critical roles in cell physiology and pathology. ءClp̕s are a class of ATP dependent serine proteases which are composed of a protease (ClpP) and an ATPase (ClpA or ClpX) component. Their involvements in degrading proteins are especially implicated und...
Molecular recognition of poly(A) by small ligands: an alternative method of analysis reveals nanomolar, cooperative and shape-selective binding Persil Çetinkol, Özgül (Oxford University Press (OUP), 2009-02-01) A few drug-like molecules have recently been found to bind poly(A) and induce a stable secondary structure (T(m)approximate to 60 degrees C), even though this RNA homopolymer is single-stranded in the absence of a ligand. Here, we report results from experiments specifically designed to explore the association of small molecules with poly(A). We demonstrate that coralyne, the first small molecule discovered to bind poly(dA), binds with unexpectedly high affinity (K(a) >10(7) M(-1)), and that the crescent sh...
Transcriptional analysis of hydrogenase genes in rhodobacter sphaeroides O.U.001 Doğrusöz, Nihal; Gündüz, Ufuk; Department of Biology (2004) In photosynthetic non-sulphur bacteria, hydrogen production is catalyzed by nitrogenases and hydrogenases. Hydrogenases are metalloenzymes that are basically classified into: the Fe hydrogenases, the Ni-Fe hydrogenases and metal-free hydrogenases. Two distinct Ni-Fe hydrogenases are described as uptake hydrogenases and bidirectional hydrogenases. The uptake hydrogenases are membrane bound dimeric enzymes consisting of small (hupS) and large (hupL) subunits, and are involved in uptake and the recycling of hy...

Citation Formats

Y. Öztürk, “Characterisation of the genetically modified cytochrome systems and their application to biohydrogen production in rhodobacter capsulatus,” Ph.D. - Doctoral Program, Middle East Technical University, 2005.