Publications by authors named "Sinan Al-Attar"

4 Publications

  • Page 1 of 1

Cytochrome bd Displays Significant Quinol Peroxidase Activity.

Sci Rep 2016 06 9;6:27631. Epub 2016 Jun 9.

Department of Biotechnology, Delft University of Technology, The Netherlands.

Cytochrome bd is a prokaryotic terminal oxidase that catalyses the electrogenic reduction of oxygen to water using ubiquinol as electron donor. Cytochrome bd is a tri-haem integral membrane enzyme carrying a low-spin haem b558, and two high-spin haems: b595 and d. Here we show that besides its oxidase activity, cytochrome bd from Escherichia coli is a genuine quinol peroxidase (QPO) that reduces hydrogen peroxide to water. The highly active and pure enzyme preparation used in this study did not display the catalase activity recently reported for E. coli cytochrome bd. To our knowledge, cytochrome bd is the first membrane-bound quinol peroxidase detected in E. coli. The observation that cytochrome bd is a quinol peroxidase, can provide a biochemical basis for its role in detoxification of hydrogen peroxide and may explain the frequent findings reported in the literature that indicate increased sensitivity to hydrogen peroxide and decreased virulence in mutants that lack the enzyme.
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http://dx.doi.org/10.1038/srep27631DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4899803PMC
June 2016

An electrogenic nitric oxide reductase.

FEBS Lett 2015 Jul 3;589(16):2050-7. Epub 2015 Jul 3.

Department of Biotechnology, Delft University of Technology, Julianalaan 67, 2628 BC, The Netherlands. Electronic address:

Nitric oxide reductases (Nors) are members of the heme-copper oxidase superfamily that reduce nitric oxide (NO) to nitrous oxide (N₂O). In contrast to the proton-pumping cytochrome oxidases, Nors studied so far have neither been implicated in proton pumping nor have they been experimentally established as electrogenic. The copper-A-dependent Nor from Bacillus azotoformans uses cytochrome c₅₅₁ as electron donor but lacks menaquinol activity, in contrast to our earlier report (Suharti et al., 2001). Employing reduced phenazine ethosulfate (PESH) as electron donor, the main NO reduction pathway catalyzed by Cu(A)Nor reconstituted in liposomes involves transmembrane cycling of the PES radical. We show that Cu(A)Nor reconstituted in liposomes generates a proton electrochemical gradient across the membrane similar in magnitude to cytochrome aa₃, highlighting that bacilli using Cu(A)Nor can exploit NO reduction for increased cellular ATP production compared to organisms using cNor.
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http://dx.doi.org/10.1016/j.febslet.2015.06.033DOI Listing
July 2015

Clustered regularly interspaced short palindromic repeats (CRISPRs): the hallmark of an ingenious antiviral defense mechanism in prokaryotes.

Biol Chem 2011 Apr 7;392(4):277-89. Epub 2011 Feb 7.

Laboratory of Microbiology, Wageningen University, Dreijenplein 10, Wageningen, The Netherlands.

Many prokaryotes contain the recently discovered defense system against mobile genetic elements. This defense system contains a unique type of repetitive DNA stretches, termed Clustered Regularly Interspaced Short Palindromic Repeats (CRISPRs). CRISPRs consist of identical repeated DNA sequences (repeats), interspaced by highly variable sequences referred to as spacers. The spacers originate from either phages or plasmids and comprise the prokaryotes' 'immunological memory'. CRISPR-associated (cas) genes encode conserved proteins that together with CRISPRs make-up the CRISPR/Cas system, responsible for defending the prokaryotic cell against invaders. CRISPR-mediated resistance has been proposed to involve three stages: (i) CRISPR-Adaptation, the invader DNA is encountered by the CRISPR/Cas machinery and an invader-derived short DNA fragment is incorporated in the CRISPR array. (ii) CRISPR-Expression, the CRISPR array is transcribed and the transcript is processed by Cas proteins. (iii) CRISPR-Interference, the invaders' nucleic acid is recognized by complementarity to the crRNA and neutralized. An application of the CRISPR/Cas system is the immunization of industry-relevant prokaryotes (or eukaryotes) against mobile-genetic invasion. In addition, the high variability of the CRISPR spacer content can be exploited for phylogenetic and evolutionary studies. Despite impressive progress during the last couple of years, the elucidation of several fundamental details will be a major challenge in future research.
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http://dx.doi.org/10.1515/BC.2011.042DOI Listing
April 2011

Distribution of CFTR variations in an Indonesian enteric fever cohort.

Clin Infect Dis 2010 May;50(9):1231-7

Department of Infectious Diseases, Leiden University Medical Center, Leiden, the Netherlands.

Background: Enteric fever is defined by circulating Salmonella serotype Typhi or Paratyphi in the blood. The first step in developing enteric fever is internalization of salmonellae in the gut epithelium. In in vitro experiments, attachment of S. Typhi to the cystic fibrosis transmembrane conductance regulator (CFTR) on the intestinal mucosa is crucial for bacterial uptake. We recently found a microsatellite polymorphism in the CFTR gene, IVS8CA, to be associated with susceptibility to enteric fever in a case-control study in Indonesia.

Methods: To determine which functional variation in CFTR is associated with susceptibility to enteric fever, we sequenced all 27 exons of the CFTR gene in 25 individuals from Indonesia. Polymorphisms that occurred more than once were genotyped in the full enteric fever cohort of 116 case patients and 322 control subjects.

Results: We identified 12 variants in, or adjacent to, the exons: 1 novel variant (L435V), 3 known mutations (N287K, I556V, Q1352H), and 8 known polymorphisms. Variations that occurred more than once were genotyped in the full cohort. The IVS8 TG(11)TG(12) genotype appears to provide some protection from acquiring enteric fever: having this protective genotype or a variation that is known to affect CFTR protein expression provides modest protection from enteric fever (odds ratio, 0.57; 95% confidence interval, 0.37-0.87; P<.01).

Conclusions: The findings demonstrate that a correlation exists between variations in the CFTR gene and protection from enteric fever. The IVS8CA polymorphism that was identified previously may, however, be the principal functional variation causing the difference in susceptibility.
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http://dx.doi.org/10.1086/651598DOI Listing
May 2010
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