scholarly journals Characterization of Auxin Conjugates in Arabidopsis. Low Steady-State Levels of Indole-3-Acetyl-Aspartate, Indole-3-Acetyl-Glutamate, and Indole-3-Acetyl-Glucose

2000 ◽  
Vol 123 (2) ◽  
pp. 589-596 ◽  
Author(s):  
Yuen Yee Tam ◽  
Ephraim Epstein ◽  
Jennifer Normanly
Keyword(s):  
Steady State ◽  
Auxin Conjugates ◽  
Steady State Levels

scholarly journals Functional characterization of the human tRNA methyltransferases TRMT10A and TRMT10B

2020 ◽  
Vol 48 (11) ◽  
pp. 6157-6169 ◽  
Author(s):  
Elisa Vilardo ◽  
Fabian Amman ◽  
Ursula Toth ◽  
Annika Kotter ◽  
Mark Helm ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Steady State ◽  
Human Genome ◽  
Functional Significance ◽  
Functional Characterization ◽  
Trna Methyltransferase ◽  
Steady State Levels

Abstract The TRM10 family of methyltransferases is responsible for the N1-methylation of purines at position 9 of tRNAs in Archaea and Eukarya. The human genome encodes three TRM10-type enzymes, of which only the mitochondrial TRMT10C was previously characterized in detail, whereas the functional significance of the two presumably nuclear enzymes TRMT10A and TRMT10B remained unexplained. Here we show that TRMT10A is m1G9-specific and methylates a subset of nuclear-encoded tRNAs, whilst TRMT10B is the first m1A9-specific tRNA methyltransferase found in eukaryotes and is responsible for the modification of a single nuclear-encoded tRNA. Furthermore, we show that the lack of G9 methylation causes a decrease in the steady-state levels of the initiator tRNAiMet-CAT and an alteration in its further post-transcriptional modification. Our work finally clarifies the function of TRMT10A and TRMT10B in vivo and provides evidence that the loss of TRMT10A affects the pool of cytosolic tRNAs required for protein synthesis.

scholarly journals Expression and characterization of a human pyruvate carboxylase variant by retroviral gene transfer

2003 ◽  
Vol 370 (1) ◽  
pp. 275-282 ◽  
Author(s):  
Mary Anna CARBONE ◽  
Brian H. ROBINSON
Keyword(s):  
Steady State ◽  
Pyruvate Carboxylase ◽  
Expression System ◽  
Type A ◽  
Immunoblot Analysis ◽  
Retroviral Gene Transfer ◽  
Reverse Transcription Pcr ◽  
Steady State Levels ◽  
The Stability

Type A pyruvate carboxylase (PC) deficiency presents mainly in the Amerindian population, specifically the Ojibwa, Cree and Micmac tribes of the Algonquin-speaking peoples. The gene for PC contains a homozygous founder mutation (G1828→A) that results in an Ala610→Thr amino acid substitution in Ojibwa with Type A PC deficiency. The mutation is located in the highly conserved pyruvate-binding domain of PC. The present paper describes a retroviral expression system for human PC used to analyse the effects of this mutation. We show, through immunoblot analysis, PC enzyme activity assays, reverse-transcription PCR and mitochondrial-import experiments, that this mutation is disease-causing in the Ojibwa population owing to its decreased catalytic activity, decreased steady-state levels of expression and inefficient import into the mitochondria. Our data suggest that this mutation may affect the stability of the protein, resulting in decreased steady-state levels of expression, and that it may also affect the secondary structure of the protein during the import process, thereby inhibiting proper translocation into the mitochondria, where PC is active.

scholarly journals Characterization of the calcium-sequestering process associated with human platelet intracellular membranes isolated by free-flow electrophoresis

1984 ◽  
Vol 222 (2) ◽  
pp. 413-417 ◽  
Author(s):  
S Menashi ◽  
K S Authi ◽  
F Carey ◽  
N Crawford
Keyword(s):  
Steady State ◽  
Human Platelet ◽  
State Level ◽  
Free Flow ◽  
Ionophore A23187 ◽  
Steady State Level ◽  
Uptake Process ◽  
Steady State Levels ◽  
Gradient Fractionation

By using density-gradient fractionation and high-voltage free-flow electrophoresis, human platelet membranes were separated into highly purified subfractions of surface (SM) and intracellular (IM) origin. Associated exclusively with the IM fraction is an ATP-dependent Ca2+ uptake that, in the absence of oxalate, reaches steady-state levels in 5-10 min. When Ca2+-EGTA buffers were used to control the external Ca2+ concentrations (range 0.1-50 microM) there was an increase in the intravesicle steady-state level of Ca2+ up to 10 microM external Ca2+ concentration. Above this level the intravesicle space becomes saturated at a concentration between 10 and 20 nmol of Ca2+ X (mg of protein)-1. The ionophore A23187 promotes a rapid and almost total release of the sequestered Ca2+ (greater than 90%, t1/2 1-2 min). The presence of oxalate in the external medium greatly enhances the Ca2+ accumulation to levels as high as 200 nmol X (mg of protein)-1, but the uptake process is more variable and rarely reaches steady-state level even after 2 h incubation. Moreover, accumulation in the presence of oxalate effects ionophore release with less than 80% depletion in 45-60 min. These findings, taken together with the known presence in the platelet of a wide variety of functional and metabolic processes triggered by this cation, suggest that the platelet IM has a key role in controlling cytosolic Ca2+ concentrations.

scholarly journals Characterization of the Proteasome Accessory Factor (paf) Operon in Mycobacterium tuberculosis

2007 ◽  
Vol 189 (8) ◽  
pp. 3044-3050 ◽  
Author(s):  
Richard A. Festa ◽  
Michael J. Pearce ◽  
K. Heran Darwin
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Steady State ◽  
Unknown Function ◽  
The Other ◽  
Accessory Factor ◽  
Reactive Nitrogen Intermediates ◽  
Steady State Levels ◽  
The Stability ◽  
Transposon Insertions

ABSTRACT In a previous screen for Mycobacterium tuberculosis mutants that are hypersusceptible to reactive nitrogen intermediates (RNI), two genes associated with the M. tuberculosis proteasome were identified. One of these genes, pafA (proteasome accessory factor A), encodes a protein of unknown function. In this work, we determined that pafA is in an operon with two additional genes, pafB and pafC. In order to assess the contribution of these genes to RNI resistance, we isolated mutants with transposon insertions in pafB and pafC. In contrast to the pafA mutant, the pafB and pafC mutants were not severely sensitized to RNI, but pafB and pafC were nonetheless required for full RNI resistance. We also found that PafB and PafC interact with each other and that each is likely required for the stability of the other protein in M. tuberculosis. Finally, we show that the presence of PafA, but not PafB or PafC, regulates the steady-state levels of three proteasome substrates. Taken together, these data demonstrate that PafA, but not PafB or PafC, is critical for maintaining the steady-state levels of known proteasome substrates, whereas all three proteins appear to play a role in RNI resistance.

Steady-state Characterization of LLC-based Single-Stage AC/DC Converter Based on Numerical Analysis

2021 ◽  
pp. 1-1
Author(s):  
Xiang Li ◽  
Liuniu Guo ◽  
Tianchen Lang ◽  
Daorong Lu ◽  
Khalil Alluhaybi ◽  
...  
Keyword(s):  
Steady State ◽  
Numerical Analysis ◽  
Single Stage
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