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71.
Zaira Aversa Thomas A. White Amanda A. Heeren Cassondra A. Hulshizer Dominik Saul Xu Zhang Anthony J. A. Molina Leanne M. Redman Corby K. Martin Susan B. Racette Kim M. Huffman Manjushri Bhapkar Sundeep Khosla Sai Krupa Das Roger A. Fielding Elizabeth J. Atkinson Nathan K. LeBrasseur 《Aging cell》2024,23(2):e14038
Calorie restriction (CR) with adequate nutrient intake is a potential geroprotective intervention. To advance this concept in humans, we tested the hypothesis that moderate CR in healthy young-to-middle-aged individuals would reduce circulating biomarkers of cellular senescence, a fundamental mechanism of aging and aging-related conditions. Using plasma specimens from the Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy (CALERIE™) phase 2 study, we found that CR significantly reduced the concentrations of several senescence biomarkers at 12 and 24 months compared to an ad libitum diet. Using machine learning, changes in biomarker concentrations emerged as important predictors of the change in HOMA-IR and insulin sensitivity index at 12 and 24 months, and the change in resting metabolic rate residual at 12 months. Finally, using adipose tissue RNA-sequencing data from a subset of participants, we observed a significant reduction in a senescence-focused gene set in response to CR at both 12 and 24 months compared to baseline. Our results advance the understanding of the effects of CR in humans and further support a link between cellular senescence and metabolic health. 相似文献
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73.
Transcriptomic Profiling of Human Pluripotent Stem Cell-derived Retinal Pigment Epithelium over Time
74.
Substrate Specificity of and Product Formation by Muconate Cycloisomerases: an Analysis of Wild-Type Enzymes and Engineered Variants 总被引:2,自引:1,他引:2 下载免费PDF全文
Martin Dominik Vollmer Helga Hoier Hans-Jürgen Hecht Ursula Schell Janosch Grning Adrian Goldman Michael Schlmann 《Applied microbiology》1998,64(9):3290-3299
Muconate cycloisomerases play a crucial role in the bacterial degradation of aromatic compounds by converting cis,cis-muconate, the product of catechol ring cleavage, to (4S)-muconolactone. Chloromuconate cycloisomerases catalyze both the corresponding reaction and a dehalogenation reaction in the transformation of chloroaromatic compounds. This study reports the first thorough examination of the substrate specificity of the muconate cycloisomerases from Pseudomonas putida PRS2000 and Acinetobacter “calcoaceticus” ADP1. We show that they transform, in addition to cis,cis-muconate, 3-fluoro-, 2-methyl-, and 3-methyl-cis,cis-muconate with high specificity constants but not 2-fluoro-, 2-chloro-, 3-chloro-, or 2,4-dichloro-cis,cis-muconate. Based on known three-dimensional structures, variants of P. putida muconate cycloisomerase were constructed by site-directed mutagenesis to contain amino acids found in equivalent positions in chloromuconate cycloisomerases. Some of the variants had significantly increased specificity constants for 3-chloro- or 2,4-dichloromuconate (e.g., A271S and I54V showed 27- and 22-fold increases, respectively, for the former substrate). These kinetic improvements were not accompanied by a change from protoanemonin to cis,cis-dienelactone as the product of 3-chloro-cis,cis-muconate conversion. The rate of 2-chloro-cis,cis-muconate turnover was not significantly improved, nor was this compound dehalogenated to any significant extent. However, the direction of 2-chloro-cis,cis-muconate cycloisomerization could be influenced by amino acid exchange. While the wild-type enzyme discriminated only slightly between the two possible cycloisomerization directions, some of the enzyme variants showed a strong preference for either (+)-2-chloro- or (+)-5-chloromuconolactone formation. These results show that the different catalytic characteristics of muconate and chloromuconate cycloisomerases are due to a number of features that can be changed independently of each other. 相似文献
75.
The consensus concept for thermostability engineering of proteins: further proof of concept 总被引:13,自引:0,他引:13
Lehmann M Loch C Middendorf A Studer D Lassen SF Pasamontes L van Loon AP Wyss M 《Protein engineering》2002,15(5):403-411
Previously, we calculated a consensus amino acid sequence from 13 homologous fungal phytases. A synthetic gene was constructed and recombinantly expressed. Surprisingly, consensus phytase-1 was 15-26 degrees C more thermostable than all parent phytases used in its design [Lehmann et al. (2000)Protein Eng., 13, 49-57]. In the present study, inclusion of six further phytase sequences in the amino acid sequence alignment resulted in the replacement of 38 amino acid residues in either one or both of the new consensus phytases-10 and -11. Since consensus phytase-10, again, was 7.4 degrees C more thermostable than consensus phytase-1, the thermostability effects of most of the 38 amino acid substitutions were tested by site-directed mutagenesis. Both stabilizing and destabilizing mutations were identified, but all affected the stability of the enzyme by <3 degrees C. The combination of all stabilizing amino acid exchanges in a multiple mutant of consensus phytase-1 increased the unfolding temperature from 78.0 to 88.5 degrees C. Likewise, back-mutation of four destabilizing amino acids and introduction of an additional stabilizing amino acid in consensus phytase-10 further increased the unfolding temperature from 85.4 to 90.4 degrees C. The thermostabilization achieved is the result of a combination of slight improvements from multiple amino acid exchanges rather than being the effect of a single or of just a few dominating mutations that have been introduced by chance. The present findings support the general validity of the consensus concept for thermostability engineering of proteins. 相似文献
76.
An amphipathic cyclic tetrapeptide scaffold containing halogenated β2,2‐amino acids with activity against multiresistant bacteria 下载免费PDF全文
Marianne H. Paulsen Eskil André Karlsen Dominik Ausbacher Trude Anderssen Annette Bayer Philipp Ochtrop Christian Hedberg Tor Haug Johanna U. Ericson Sollid Morten B. Strøm 《Journal of peptide science》2018,24(10)
The present study describes the synthesis and biological studies of a small series of head‐to‐tail cyclic tetrapeptides of the general structure c(Lys‐β2,2‐Xaa‐Lys) containing one lipophilic β2,2‐amino acid and Lys, Gly, Ala, or Phe as the Xaa residue in the sequence. The peptides were investigated for antimicrobial activity against gram‐positive and gram‐negative reference strains and 30 multiresistant clinical isolates including strains with extended spectrum β‐lactamase—carbapenemase (ESBL‐CARBA) production. Toxicity was determined against human red blood cells. The most potent peptides showed high activity against the gram‐positive clinical isolates with minimum inhibitory concentrations of 4–8 μg/mL and low haemolytic activity. The combination of high antimicrobial activity and low toxicity shows that these cyclic tetrapeptides containing lipophilic β2,2‐amino acids form a valuable scaffold for designing novel antimicrobial agents. 相似文献
77.
Martin Kemler María P. Martín M. Teresa Telleria Angela M. Schäfer Andrey Yurkov Dominik Begerow 《Organisms Diversity & Evolution》2013,13(2):111-126
Anther smuts in the genus Microbotryum often show very high host specificity toward their caryophyllaceous hosts, but some of the larger host groups such as Dianthus are crucially undersampled for these parasites so that the question of host specificity cannot be answered conclusively. In this study we sequenced the internal transcribed spacer (ITS) region of members of the Microbotryum dianthorum species complex as well as their Dianthus hosts. We compared phylogenetic trees of these parasites including sequences of anther smuts from other Caryophyllaceae, mainly Silene, with phylogenies of Caryophyllaceae that are known to harbor anther smuts. Additionally we tested whether observed patterns in parasites are due to shared ancestry or if geographic separation is a factor that should be taken into consideration in delimitating species. Parasites on Dianthus showed mainly an arbitrary distribution on Dianthus hosts, whereas parasites on other Caryophyllaceae formed well-supported monophyletic clades that corresponded to restricted host groups. The same pattern was observed in the Caryophyllaceae studied: morphologically described Dianthus species did not correspond well with monophyletic clades based on molecular data, whereas other Caryophyllaceae mainly did. We suggest that these different patterns primarily result from different breeding systems and speciation times between different host groups as well as difficulties in species delimitations in the genus Dianthus. 相似文献
78.
79.
Abdelmohsen K Sauerbier E Ale-Agha N Beier J Walter P Galban S Stuhlmann D Sies H Klotz LO 《Biochemical and biophysical research communications》2007,364(2):313-317
Extracellular signal-regulated kinases (ERK) 1 and 2 as well as ERK-5 were previously suggested to phosphorylate connexin-43 and to contribute to the modulation of gap junctional intercellular communication (GJC). Exposure of rat liver epithelial cells to epidermal growth factor (EGF) or the redox cycling and alkylating agent menadione resulted in phosphorylation of connexin-43 and loss in GJC, both of which were abrogated by pharmacological inhibitors of ERK-1/2 activation, if used in concentrations that selectively abrogate phosphorylation of ERK-1/2 but not of ERK-5. Thus, EGF- or menadione-induced loss of GJC is mediated by ERK-1/2 but not ERK-5 in rat liver epithelial cells. 相似文献
80.
Quantification of optic disc edema during exposure to high altitude shows no correlation to acute mountain sickness 总被引:1,自引:0,他引:1
Willmann G Fischer MD Schatz A Schommer K Messias A Zrenner E Bartz-Schmidt KU Gekeler F 《PloS one》2011,6(11):e27022