scholarly journals The equilibrium assumption is valid for the kinetic treatment of most time-dependent protein-modification reactions

1979 ◽  
Vol 183 (3) ◽  
pp. 771-771
Keyword(s):  
Protein Modification ◽  
Time Dependent ◽  
Dependent Protein ◽  
Kinetic Treatment

scholarly journals The equilibrium assumption is valid for the kinetic treatment of most time-dependent protein-modification reactions

1979 ◽  
Vol 181 (3) ◽  
pp. 775-778 ◽  
Author(s):  
K Brocklehurst
Keyword(s):  
Rate Constant ◽  
Protein Modification ◽  
Order Rate Constant ◽  
Time Dependent ◽  
Quasi Equilibrium ◽  
Dependent Inhibition ◽  
Dependent Protein ◽  
Time Dependent Inhibition ◽  
Kinetics Of ◽  
Kinetic Treatment

To facilitate mechanistic interpretation of the kinetics of time-dependent inhibition of enzymes and of similar protein modification reactions, it is important to know when the equilibrium assumption may be applied to the model: formula: (see text). The conventional criterion of quasi-equilibrium, k + 2 less than k-1, is not always easy to assess, particularly when k + 2 cannot be separately determined. It is demonstrated that the condition k + 2 less than k-1 is necessarily true, however, when the value of the apparent second-order rate constant for the modification reaction is much smaller than the value of k + 1. Since k + 1 is commonly at least 10(7)M-1.S-1 for substrates, it is probable that the equilibrium assumption may be properly applied to most irreversible inhibitions and modification reactions.

Abstract 391: Sterol Efflux Function and Protein Composition of HDL Associates With Recovery From Stroke

2017 ◽  
Vol 37 (suppl_1) ◽  
Author(s):  
Deanna Plubell ◽  
Alexandra Fenton ◽  
Clark Wayne ◽  
Neil A Zakai ◽  
Joseph F Quinn ◽  
...  
Keyword(s):  
Stroke Risk ◽  
Protein Composition ◽  
Hdl Cholesterol ◽  
Time Dependent ◽  
Stroke Recovery ◽  
Control Group ◽  
Post Stroke ◽  
Dependent Protein ◽  
Meta Analyses ◽  
The Relationship

Background: Prospective cohort studies and meta-analyses examining the relationship between HDL-cholesterol (C) and stroke are discordant and question the value of HDL-C as a marker for stroke risk prediction. Other properties of HDL-C such as cholesterol efflux capacity (CEC) and proteome, are less studied. Methods: We investigated the changes in HDL CEC and proteome to determine if they are associated with improved stroke recovery. Plasma from age- and lipid profile-matched healthy controls (N = 35) and stroke patients were collected at 24 (early, N = 35) and 96 hour (late, N = 20) post stroke, and analyzed with three independent assays to measure macrophage-mediated, ABCA1 and ABCG1-specific sterol efflux, and HDL proteome. Stroke recovery was assessed at 3 months using the Modified Rankin Scores (MRS) and the NIH Stroke Scale (NIHSS). Results: Both macrophage- and ABCG1-mediated CEC were reduced by 50% ( P <0.0001) and 20% ( P <0.038) in early and late post stroke samples, respectively, compared to the control group. Patients who had comparable or increased CEC between the two-time points exhibited lower NIHSS and MRS indicating better recovery. Proteomic analysis of HDL indicated a distinct time-dependent remodeling post stroke. Coagulation complement cascade proteins (FGB, FGA, A2M, C3) significantly increased (FDR>0.01) early and returned to control levels later, inflammation proteins (SAA1, SAA2, PON1, C4B) increased early and continued to increase. Interestingly, platelet adhesion proteins (DSG1, JUP, ITGB1, ITGA2, TUBB, DNAH3, PF4) were abundantly present in only later samples. Conclusion: 1) patients who maintain or improve HDL CEC post stroke exhibit better recovery scores, 2) post stroke HDL proteome remodeling is dynamic with distinct time-dependent protein signatures that may associate with stroke recovery.

Time-dependent, protein-directed growth of gold nanoparticles within a single crystal of lysozyme

2011 ◽  
Vol 6 (2) ◽  
pp. 93-97 ◽  
Author(s):  
Hui Wei ◽  
Zidong Wang ◽  
Jiong Zhang ◽  
Stephen House ◽  
Yi-Gui Gao ◽  
...  
Keyword(s):  
Gold Nanoparticles ◽  
Single Crystal ◽  
Time Dependent ◽  
Dependent Protein ◽  
Directed Growth

scholarly journals Activation and phosphorylation of the ‘dense-vesicle’ high-affinity cyclic AMP phosphodiesterase by cyclic AMP-dependent protein kinase

1989 ◽  
Vol 260 (1) ◽  
pp. 27-36 ◽  
Author(s):  
E Kilgour ◽  
N G Anderson ◽  
M D Houslay
Keyword(s):  
Protein Kinase ◽  
Cyclic Amp ◽  
Time Dependent ◽  
Dependent Protein Kinase ◽  
High Affinity ◽  
Catalytic Unit ◽  
Dependent Protein ◽  
Membrane Extract ◽  
Pre Treatment ◽  
Vesicle Cycle

Incubation of a hepatocyte particulate fraction with ATP and the isolated catalytic unit of cyclic AMP-dependent protein kinase (A-kinase) selectively activated the high-affinity ‘dense-vesicle’ cycle AMP phosphodiesterase. Such activation only occurred if the membranes had been pre-treated with Mg2+. Mg2+ pre-treatment appeared to function by stimulating endogenous phosphatases and did not affect phosphodiesterase activity. Using the antiserum DV4, which specifically immunoprecipitated the 51 and 57 kDa components of the ‘dense-vesicle’ phosphodiesterase from a detergent-solubilized membrane extract, we isolated a 32P-labelled phosphoprotein from 32P-labelled hepatocytes. MgCl2 treatment of such labelled membranes removed 32P from the immunoprecipitated protein. Incubation of the Mg2+-pre-treated membranes with [32P]ATP and A-kinase led to the time-dependent incorporation of label into the ‘dense-vesicle’ phosphodiesterase, as detected by specific immunoprecipitation with the antiserum DV4. The time-dependences of phosphodiesterase activation and incorporation of label were similar. It is suggested (i) that phosphorylation of the ‘dense-vesicle’ phosphodiesterase by A-kinase leads to its activation, and that such a process accounts for the ability of glucagon and other hormones, which increase intracellular cyclic AMP concentrations, to activate this enzyme, and (ii) that an as yet unidentified kinase can phosphorylate this enzyme without causing any significant change in enzyme activity but which prevents activation and phosphorylation of the phosphodiesterase by A-kinase.

scholarly journals The Corepressor mSin3A Regulates Phosphorylation-Induced Activation, Intranuclear Location, and Stability of AML1

2004 ◽  
Vol 24 (3) ◽  
pp. 1033-1043 ◽  
Author(s):  
Yoichi Imai ◽  
Mineo Kurokawa ◽  
Yuko Yamaguchi ◽  
Koji Izutsu ◽  
Eriko Nitta ◽  
...  
Keyword(s):  
Transcription Factors ◽  
Protein Modification ◽  
Transcriptional Activity ◽  
Regulatory Mechanism ◽  
Dna Binding Protein ◽  
Time Dependent ◽  
Myeloid Differentiation ◽  
Dependent Manner ◽  
Extracellular Signal Regulated Kinase ◽  
Extracellular Signal

ABSTRACT The AML1 (RUNX1) gene, one of the most frequent targets of translocations associated with human leukemias, encodes a DNA-binding protein that plays pivotal roles in myeloid differentiation through transcriptional regulation of various genes. Previously, we reported that AML1 is phosphorylated on two serine residues with dependence on activation of extracellular signal-regulated kinase, which positively regulates the transcriptional activity of AML1. Here, we demonstrate that the interaction between AML1 and the corepressor mSin3A is regulated by phosphorylation of AML1 and that release of AML1 from mSin3A induced by phosphorylation activates its transcriptional activity. Furthermore, phosphorylation of AML1 regulates its intranuclear location and disrupts colocalization of AML1 with mSin3A in the nuclear matrix. PEBP2β/CBFβ, a heterodimeric partner of AML1, was shown to play a role in protecting AML1 from proteasome-mediated degradation. We show that mSin3A also protects AML1 from proteasome-mediated degradation and that phosphorylation-induced release of AML1 from mSin3A results in degradation of AML1 in a time-dependent manner. This study provides a novel regulatory mechanism for the function of transcription factors mediated by protein modification and interaction with cofactors.

scholarly journals The Metabolic Chemical Reporter Ac46AzGal Could Incorporate Intracellular Protein Modification in the Form of UDP-6AzGlc Mediated by OGT and Enzymes in the Leloir Pathway

2021 ◽  
Vol 9 ◽  
Author(s):  
Jiajia Wang ◽  
Biao Dou ◽  
Lu Zheng ◽  
Wei Cao ◽  
Peiyu Dong ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Protein Modification ◽  
Time Dependent ◽  
Dependent Manner ◽  
Intracellular Protein ◽  
Galactose Metabolism ◽  
Naturally Occurring ◽  
Leloir Pathway ◽  
Chemical Reporter ◽  
Complex Glycans

Galactose is a naturally occurring monosaccharide used to build complex glycans that has not been targeted for labeling as a metabolic reporter. Here, we characterize the cellular modification of proteins by using Ac46AzGal in a dose- and time-dependent manner. It is noted that a vast majority of this labeling of Ac46AzGal occurs intracellularly in a range of mammalian cells. We also provided evidence that this labeling is dependent on not only the enzymes of OGT responsible for O-GlcNAcylation but also the enzymes of GALT and GALE in the Leloir pathway. Notably, we discover that Ac46AzGal is not the direct substrate of OGT, and the labeling results may attribute to UDP-6AzGlc after epimerization of UDP-6AzGal via GALE. Together, these discoveries support the conclusion that Ac46AzGal as an analogue of galactose could metabolically label intracellular O-glycosylation modification, raising the possibility of characterization with impaired functions of the galactose metabolism in the Leloir pathway under certain conditions, such as galactosemias.

Glutathionylation of fibronectin records mechanical history, priming an integrin switch and myofibroblast polarization

2021 ◽  
Author(s):  
Wei Li ◽  
Leandro Moretti ◽  
Chiuan-Ren Yeh ◽  
Matthew Torres ◽  
Thomas Barker
Keyword(s):  
Conformational Changes ◽  
Posttranslational Modifications ◽  
Protein Modification ◽  
Polymer Network ◽  
Integrin Receptors ◽  
Post Translational Modifications ◽  
Cell Behaviors ◽  
Predominant Component ◽  
Physical Information ◽  
Dependent Protein

Abstract The extracellular matrix (ECM) is a protein polymer network that physically supports cells within a tissue and also acts as an important biochemical stimulus directing cell behaviors. For fibronectin, a predominant component of the ECM, these physical and biochemical activities are inextricably linked as physical forces trigger conformational changes that impact its biochemical activity. We analyzed whether oxidative post-translational modifications, specifically glutathionylation, enable fibronectin to ‘record’ physical information through stretch-dependent protein modification. Posttranslational modifications of the ECM are understudied, but represent opportunities for time- or stimuli-dependent changes in structure-function relationships that both persist over time and could have dominant impacts on cell-ECM homeostasis. We provide direct evidence that stretch-dependent glutathionylation of fibronectin irreversibly and significantly alters its mechanical properties with concomitant changes in the binding of integrin receptors and downstream cell signaling events. Stretch-dependent glutathionylation of fibronectin could have significant impact on the balance between tissue homeostasis and pathological progression, particularly in tissues and organs that are exposed to high oxidative stress, such as the lung.

Morphogenetic disturbances from timed inhibitions of protein synthesis in Fundulus

Development ◽  
1973 ◽  
Vol 29 (2) ◽  
pp. 363-382
Author(s):  
Richard B. Crawford ◽  
Charles E. Wilde ◽  
Murk H. Heinemann ◽  
F. J. Hendler
Keyword(s):  
Protein Synthesis ◽  
Serial Order ◽  
Time Dependent ◽  
Amino Acid Incorporation ◽  
Active Expression ◽  
Dependent Protein ◽  
Early Zygote ◽  
The Times ◽  
Cleavage Failure ◽  
Ribosomal Complex

The reversible inhibition of protein synthesis at the 75–95% level in the early zygote of Fundulus results in a specific series of developmental failures dependent upon the times of inhibitor pulse initiation. The severity of the morphogenetic failure is inversely related to the time of initiation and directly to the length of the pulse. The defects reflect the time dependent serial order of events in morphogenesis. The defects range from failure of cleavage through disorders of blastulation, failure of axiation, anencephaly to microcephaly and are entirely predictable. With the exception of cleavage failure the pattern is identical with that found using pulses of actinomycin D in a similar manner. The agent used was pactamycin, an antibiotic which reversibly inhibits amino acid incorporation into protein by disturbing the assembly of the functional ribosomal complex. The significance of time dependent protein synthesis as an active expression in morphogenesis of similarly time dependent information flow via RNA synthesis is discussed.

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