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'Site Directed Mutagenesis' in keywords
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2001 (1)
1990 (2)
1Author    Wim Vermaas, Jeroen Charité, Gaozhong ShenRequires cookie*
 Title    Q a Binding to D2 Contributes to the Functional and Structural Integrity of Photosystem II  
 Abstract    Two D 2 mutants were created with a site-directed mutation near the presumable binding site of Q a. In one of the mutants, in which Trp-253, the aromatic residue potentially involved in facilitating electron transport from pheophytin to Q A and/or in binding of Q A, had been replaced by Leu, PS II was undetectable in thylakoids. This mutant is an obligate photohetero-troph. In another mutant the Gly-215 residue, located next to the His residue that is pro­ posed to bind Q a and Fe2+, was mutated to Trp. This mutation leads to a rapid inactivation of oxygen evolution capacity in the light, and to a virtual elimination of the potential to grow photoautotrophically, but does not greatly affect the number of photosystem II reaction cen­ ters on a chlorophyll basis. We propose that proper binding of Q A to the photosystem II reac­ tion center complex is a prerequisite for stability of the photosystem II complex. Impairment of Q a binding leads to rapid inactivation of photosystem II, which may be followed by a struc­ tural disintegration of the complex. 
  Reference    Z. Naturforsch. 45c, 359—365 (1990); received November 3 1989 
  Published    1990 
  Keywords    Photoinhibition, Plastoquinone, Photosynthesis, Site-Directed Mutagenesis, Cyanobacteria 
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 TEI-XML for    default:Reihe_C/45/ZNC-1990-45c-0359.pdf 
 Identifier    ZNC-1990-45c-0359 
 Volume    45 
2Author    Paxton Loke, Tiow-Suan SimRequires cookie*
 Title    Site-Directed Mutagenesis of Proline-285 to Leucine in Cephalosporium acremonium Isopenicillin N -Synthase Affects Catalysis and Increases Soluble Expression at Higher Temperatures  
 Abstract    The conversion of Ö-(L-a-aminoadipyl)-L-cysteinyl-D-valine (A C V) to isopenicillin N is de­ pendant on the catalytic action of isopenicillin N -synthase (IPNS), an important enzyme in the penicillin and cephalosporin biosynthetic pathway. One of the amino acid residues suggested by the Aspergillus nidulans IPNS crystal structure for interaction with the valine isopropyl group of ACV is proline-283. Site-directed mutagenesis of the corresponding pro­ line-285 to leucine in Cephalosporium acremonium IPNS resulted in non-measurable activity but an increased soluble expression at higher temperatures in a heterologous E. coli host. 
  Reference    Z. Naturforsch. 56c, 413 (2001); received January ll/F ebruary 14 2001 
  Published    2001 
  Keywords    Isopenicillin N -Synthase, Site-Directed Mutagenesis, Proline 
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 TEI-XML for    default:Reihe_C/56/ZNC-2001-56c-0413.pdf 
 Identifier    ZNC-2001-56c-0413 
 Volume    56 
3Author    HimadriB. Pakrasi, KarinJ. Nyhus, HowardG. RanokRequires cookie*
 Title    Targeted Deletion Mutagenesis of the ß Subunit of Cytochrome b559 Protein Destabilizes the Reaction Center of Photosystem II  
 Abstract    Oligonucleotide-directed mutagenesis techniques were used to delete the psbF gene, encod­ ing the ß subunit o f the cytochrom e b559 protein o f the photosystem II com plex in the cyano­ bacterium, Synechocystis 6803. Cyt b559 is an integral com ponent o f PS II complex. However, its precise functional role in PS II remains to be determined. Previously, we created a mutant in which the psbF gene as well as three o f its neighbouring genes, psbE , psbL and p sb i were simultaneously deleted from the chrom osom e o f Synechocystis 6803 (Pakrasi, Williams and Arntzen, EMBO J. 7, 3 2 5 -3 3 2 , 1988). This mutant had no PS II activity. However, the role o f any one o f the four individual gene products could not be determined by studying this mutant. The newly generated mutant, T 256, had only one gene, p sbF , deleted from the genome. This mutant was also impaired in its PS II activities. In addition, it had barely detectable levels o f two other protein com ponents, D1 (herbicide binding protein) and D2, o f the reaction center o f PS II, in its thylakoid membranes. In contrast, two other proteins o f PS II, CP47 and CP43 were present in appreciable amounts. Fluorescence spectra (77 K) o f the mutant showed the absence o f a peak at 695 nm that was previously believed to originate from CP47. In addition, phycobilisomes, the light-harvesting antenna system o f PS II, were found to be assembled normally in this mutant. We conclude that the presence o f the ß subunit o f Cyt b559 in the thylakoid membranes is critically important for the assembly o f PS II reaction center. 
  Reference    Z. Naturforsch. 45c, 423 (1990); received November 21 1989 
  Published    1990 
  Keywords    Photosystem II, Cytochrom e b559, Site-Directed Mutagenesis, Protein Complex Stability, Synechocystis 6803 
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 TEI-XML for    default:Reihe_C/45/ZNC-1990-45c-0423.pdf 
 Identifier    ZNC-1990-45c-0423 
 Volume    45