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991.
Noinaj N Wattanasak R Lee DY Wally JL Piszczek G Chock PB Stadtman TC Buchanan SK 《Journal of bacteriology》2012,194(2):499-508
Selenophosphate synthetase (SPS) catalyzes the synthesis of selenophosphate, the selenium donor for the biosynthesis of selenocysteine and 2-selenouridine residues in seleno-tRNA. Selenocysteine, known as the 21st amino acid, is then incorporated into proteins during translation to form selenoproteins which serve a variety of cellular processes. SPS activity is dependent on both Mg(2+) and K(+) and uses ATP, selenide, and water to catalyze the formation of AMP, orthophosphate, and selenophosphate. In this reaction, the gamma phosphate of ATP is transferred to the selenide to form selenophosphate, while ADP is hydrolyzed to form orthophosphate and AMP. Most of what is known about the function of SPS has derived from studies investigating Escherichia coli SPS (EcSPS) as a model system. Here we report the crystal structure of the C17S mutant of SPS from E. coli (EcSPS(C17S)) in apo form (without ATP bound). EcSPS(C17S) crystallizes as a homodimer, which was further characterized by analytical ultracentrifugation experiments. The glycine-rich N-terminal region (residues 1 through 47) was found in the open conformation and was mostly ordered in both structures, with a magnesium cofactor bound at the active site of each monomer involving conserved aspartate residues. Mutating these conserved residues (D51, D68, D91, and D227) along with N87, also found at the active site, to alanine completely abolished AMP production in our activity assays, highlighting their essential role for catalysis in EcSPS. Based on the structural and biochemical analysis of EcSPS reported here and using information obtained from similar studies done with SPS orthologs from Aquifex aeolicus and humans, we propose a catalytic mechanism for EcSPS-mediated selenophosphate synthesis. 相似文献
992.
Joanna Jakóbkiewicz-Banecka Ewa Piotrowska Magdalena Narajczyk Sylwia Barańska Grzegorz Węgrzyn 《Journal of biomedical science》2009,16(1):26-9
Background
Mucopolysaccharidoses (MPS) are inherited metabolic disorders caused by mutations leading to dysfunction of one of enzymes involved in degradation of glycosaminoglycans (GAGs). Due to their impaired degradation, GAGs accumulate in cells of patients, which results in dysfunction of tissues and organs. Substrate reduction therapy is one of potential treatment of these diseases. It was demonstrated previously that genistein (4', 5, 7-trihydroxyisoflavone) inhibits synthesis and reduces levels of GAGs in cultures of fibroblasts of MPS patients. Recent pilot clinical study indicated that such a therapy may be effective in MPS III (Sanfilippo syndrome). 相似文献993.
Katarzyna Kozieł Magdalena Lebiedzinska Gyorgy Szabadkai Marta Onopiuk Wojciech Brutkowski Katarzyna Wierzbicka Grzegorz Wilczyński Paolo Pinton Jerzy Duszyński Krzysztof Zabłocki Mariusz R. Wieckowski 《The international journal of biochemistry & cell biology》2009,41(12):2440-2449
A proper cooperation between the plasma membrane, the endoplasmic reticulum and the mitochondria seems to be essential for numerous cellular processes involved in Ca2+ signalling and maintenance of Ca2+ homeostasis. A presence of microsomal and mitochondrial proteins together with those characteristic for the plasma membrane in the fraction of the plasma membrane associated membranes (PAM) indicates a formation of stabile interactions between these three structures. We isolated the plasma membrane associated membranes from Jurkat cells and found its significant enrichment in the plasma membrane markers including plasma membrane Ca2+-ATPase, Na+, K+-ATPase and CD3 as well as sarco/endoplasmic reticulum Ca2+ ATPase as a marker of the endoplasmic reticulum membranes. In addition, two proteins involved in the store-operated Ca2+ entry, Orai1 located in the plasma membrane and an endoplasmic reticulum protein STIM1 were found in this fraction. Furthermore, we observed a rearrangement of STIM1-containing protein complexes isolated from Jurkat cells undergoing stimulation by thapsigargin. We suggest that the inter-membrane compartment composed of the plasma membrane and the endoplasmic reticulum, and isolated as a stabile plasma membrane associated membranes fraction, might be involved in the store-operated Ca2+ entry, and their formation and rebuilding have an important regulatory role in cellular Ca2+ homeostasis. 相似文献
994.
Grzelak A Kruszewski M Macierzyńska E Piotrowski Ł Pułaski Ł Rychlik B Bartosz G 《Cellular & molecular biology letters》2009,14(1):23-34
The erythrocytes of 12-month old Sod1
−/−
mice showed an increased level of reactive oxygen species (ROS), as estimated by the degree of dihydroethidine and dihydrorhodamine
oxidation, and the increased level of Heinz bodies. No indices of severe oxidative stress were found in the red blood cells
and blood plasma of Sod1
−/−
mice as judged from the lack of significant changes in the levels of erythrocyte and plasma glutathione, plasma protein thiol
and carbonyl groups and thiobarbituric-acid reactive substances in the blood plasma. However, a decreased erythrocyte lifespan,
increased reticulocyte count and splenomegaly were noted, indicating the importance of superoxide dismutase for maintaining
erythrocyte viability. The levels of erythrocyte ROS and Heinz bodies and the reticulocyte count were indistinguishable in
Sod1
+/+
and Sod1
+/−
mice, suggesting that a superoxide dismutase activity decrease to half of its normal value may be sufficient to secure the
protective effects of the enzyme. 相似文献
995.
J?rg U. Ganzhorn Summer Arrigo-Nelson Sue Boinski An Bollen Valentina Carrai Abigail Derby Giuseppe Donati Andreas Koenig Martin Kowalewski Petra Lahann Ivan Norscia Sandra Y. Polowinsky Christoph Schwitzer Pablo R. Stevenson Mauricio G. Talebi Chia Tan Erin R. Vogel Patricia C. Wright 《PloS one》2009,4(12)
Background
The ecological factors contributing to the evolution of tropical vertebrate communities are still poorly understood. Primate communities of the tropical Americas have fewer folivorous but more frugivorous genera than tropical regions of the Old World and especially many more frugivorous genera than Madagascar. Reasons for this phenomenon are largely unexplored. We developed the hypothesis that Neotropical fruits have higher protein concentrations than fruits from Madagascar and that the higher representation of frugivorous genera in the Neotropics is linked to high protein concentrations in fruits. Low fruit protein concentrations in Madagascar would restrict the evolution of frugivores in Malagasy communities.Methodology/Principal Findings
We reviewed the literature for nitrogen concentrations in fruits from the Neotropics and from Madagascar, and analyzed fruits from an additional six sites in the Neotropics and six sites in Madagascar. Fruits from the Neotropical sites contain significantly more nitrogen than fruits from the Madagascar sites. Nitrogen concentrations in New World fruits are above the concentrations to satisfy nitrogen requirements of primates, while they are at the lower end or below the concentrations to cover primate protein needs in Madagascar.Conclusions/Significance
Fruits at most sites in the Neotropics contain enough protein to satisfy the protein needs of primates. Thus, selection pressure to develop new adaptations for foods that are difficult to digest (such as leaves) may have been lower in the Neotropics than in Madagascar. The low nitrogen concentrations in fruits from Madagascar may contribute to the almost complete absence of frugivorous primate species on this island. 相似文献996.
The crystal structure at 2.5A resolution of the membrane-intrinsic, homotrimeric photosystem I (PSI) isolated from the thermophilic cyanobacterium Synechococcus elongatus shows that each monomer is composed of 12 protein subunits of which nine are embedded in the membrane and feature a total of 34 transmembrane alpha-helices (TMH). Hence, PSI provides an ideal case to study "conventional" and C(alpha)-H...O hydrogen bonds between TMH engaged in intra- and intersubunit interactions. Of the total of 75 C(alpha)-H...O hydrogen bonds between TMHs, 72 are intrasubunit and only three are intersubunit. The two largest subunits PsaA and PsaB are each folded into 11 TMHs showing 29 and 24 intrasubunit C(alpha)-H...O hydrogen bonds, respectively, that are not distributed randomly but many of them flank chlorophyll a (Chl a) co-ordinating amino acids, suggesting stabilisation of these structural segments. As major constituent of the trimerisation domain, subunit PsaL is located next to the 3-fold axis relating the three monomers of PSI. PsaL features a unique number of 19 intrasubunit C(alpha)-H...O hydrogen bonds that connect two of its three TMHs but there are no intersubunit C(alpha)-H...O hydrogen bonds between the three PsaL. Of the three intersubunit C(alpha)-H...O hydrogen bonds, two are formed between PsaA and PsaB and one between PsaB and PsaM. The large number of 75 C(alpha)-H...O hydrogen bonds contrasts the 49 conventional hydrogen bonds, indicating that the former and van der Waals contacts determine association and orientation of TMHs in PSI. 相似文献
997.
While the total antioxidant capacity (TAC) of blood plasma is mainly accounted for by urate, TAC of cell interior can be expected to depend more on other antioxidants, especially glutathione and protein -SH groups. We studied TAC of homogenates of several lines of cultured cells subjected to the action of thiol-modifying agents. Comparison of changes of TAC of the homogenates and of the level of total thiols (determined with a biradical spin label) demonstrates that alterations in cellular thiol content is the main determinant of changes of TAC of cell homogenates. These results show that estimation of TAC of cell extracts may be a useful parameter of assessment of oxidative stress, primarily of oxidation of thiol groups, yielding information different than TAC of body fluids. 相似文献
998.
999.
J.?David?Van?Horn Grzegorz?Bulaj David?P.?Goldenberg Cynthia?J.?BurrowsEmail author 《Journal of biological inorganic chemistry》2003,8(6):601-610
A series of peptide ligands containing the sequence -Cys-Xaa-His- (CXH; Xaa=Gly or Lys) has been prepared and the coordination chemistry of these peptides with nickel(II) investigated. Selective protection of either the N-terminal cysteine thiol or amine group gave complexes with amino or thiolato coordination, respectively, to nickel(II). Insertion of CGH into a pentapeptide, N-acetyl-Ala-Cys-Gly-His-Ala-CONH2, allowed the formation of a square-planar thiolato Cys-Gly-His complex with nickel(II) in an internal position of the peptide. Inclusion of an N-terminal cysteine residue with a free amino terminus gave rise to pH- and dioxygen-dependent coordination behavior. Solutions of CGH-CONH2 with nickel(II) at neutral pH yielded a red nickel-thiolate complex, but at higher pH (8.5 or above) or with exposure to dioxygen, yellow nickel complexes with N-terminal amino coordination were observed. The disulfide-bridged dimers formed from Ni(CGH-CONH2) in the presence of air were characterized and found to have the typical coordination found in the amino-terminal binding motif of the serum albumins. Nickel(II) coordination and thiol reactivity were also studied by determination of rates of thiol alkylation and by monitoring air oxidation in the presence of various metals. Zinc(II) effectively inhibits thiol alkylation and oxidation (disulfide formation) in all the peptides studied. Nickel(II) inhibits aerobic oxidation and alkylation of N-terminal protected peptides such as N-acetyl-Cys-Gly-His, but does not inhibit air oxidation of free amino terminal peptides such as Cys-Gly-His. Instead, nickel(II) mediates the formation an additional product under aerobic conditions, a cysteinesulfinic acid.Electronic Supplementary Material Supplementary material is available for this article if you access the article at . A link in the frame on the left on that page takes you directly to the supplementary material.Abbreviations CGH
cysteinylglycylhistidine
- GGH
glycylglycylhistidine
- Xaa
any amino acid 相似文献
1000.