Thermal Aggregation (thermal + aggregation)

Distribution by Scientific Domains


Selected Abstracts


Effect of GroEL on Thermal Aggregation of Glycogen Phosphorylase b from Rabbit Skeletal Muscle

MACROMOLECULAR BIOSCIENCE, Issue 7 2010
Tatyana B. Eronina
Abstract The suppression of the thermal aggregation of glycogen phosphorylase b (Phb) from rabbit skeletal muscle by the chaperonin GroEL is studied using dynamic light scattering. It is shown that the decrease in the rate of Phb aggregation under the action of GroEL is due to the transition of the aggregation process from the kinetic regime, wherein the rate of aggregation is limited by diffusion of the interacting particles, to a regime where the sticking probability for the colliding particles becomes lower than one (reaction-limited cluster-cluster aggregation). The analytical-ultracentrifugation data show that elevated temperatures induce dissociation of the dimeric Phb. The formation of a complex between the denatured monomeric form of Phb and the dissociated forms of GroEL is detected during heating at 46,C. [source]


Chaperone activity of recombinant maize chloroplast protein synthesis elongation factor, EF-Tu

FEBS JOURNAL, Issue 18 2004
Damodara Rao
The protein synthesis elongation factor, EF-Tu, is a protein that carries aminoacyl-tRNA to the A-site of the ribosome during the elongation phase of protein synthesis. In maize (Zea mays L) this protein has been implicated in heat tolerance, and it has been hypothesized that EF-Tu confers heat tolerance by acting as a molecular chaperone and protecting heat-labile proteins from thermal aggregation and inactivation. In this study we investigated the effect of the recombinant precursor of maize EF-Tu (pre-EF-Tu) on thermal aggregation and inactivation of the heat-labile proteins, citrate synthase and malate dehydrogenase. The recombinant pre-EF-Tu was purified from Escherichia coli expressing this protein, and mass spectrometry confirmed that the isolated protein was indeed maize EF-Tu. The purified protein was capable of binding GDP (indicative of protein activity) and was stable at 45 C, the highest temperature used in this study to test this protein for possible chaperone activity. Importantly, the recombinant maize pre-EF-Tu displayed chaperone activity. It protected citrate synthase and malate dehydrogenase from thermal aggregation and inactivation. To our knowledge, this is the first observation of chaperone activity by a plant/eukaryotic pre-EF-Tu protein. The results of this study support the hypothesis that maize EF-Tu plays a role in heat tolerance by acting as a molecular chaperone and protecting chloroplast proteins from thermal aggregation and inactivation. [source]


Calnexin inhibits thermal aggregation and neurotoxicity of prion protein

JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 2 2010
Wenxi Wang
Abstract Prion diseases are fatal neurodegenerative disorder associated with the conversion of the cellular isoform of the prion protein (PrPC) into the infectious scrapie isoform (PrPSc). Deposition of misfolded prion proteins (PrP) on certain regions of brain can result in prion diseases. As a membrane-bound chaperone of the endoplasmic reticulum (ER), calnexin ensures the proper folding and quality control of newly synthesized proteins. Using purified components in vitro, calnexin associated with many proteins and suppresses their thermal aggregation effectively. We for the first time analyzed PrP-calnexin interaction. The immunoprecipitation, confocal microscope and native polyacrylamide-gel electrophoresis results indicated that calnexin could bind PrP both in vitro and in vivo. The turbidity result showed that calnexin could supress thermal aggregation of PrP. MTT, flow cytometry (FCM) and caspase activity studies demonstrated that calnexin prevent caspase-3-mediated cytotoxicity induced by PrP. These results implied that calnexin is potentially beneficial for the resistance of prion diseases. J. Cell. Biochem. 111: 343,349, 2010. 2010 Wiley-Liss, Inc. [source]


Effect of GroEL on Thermal Aggregation of Glycogen Phosphorylase b from Rabbit Skeletal Muscle

MACROMOLECULAR BIOSCIENCE, Issue 7 2010
Tatyana B. Eronina
Abstract The suppression of the thermal aggregation of glycogen phosphorylase b (Phb) from rabbit skeletal muscle by the chaperonin GroEL is studied using dynamic light scattering. It is shown that the decrease in the rate of Phb aggregation under the action of GroEL is due to the transition of the aggregation process from the kinetic regime, wherein the rate of aggregation is limited by diffusion of the interacting particles, to a regime where the sticking probability for the colliding particles becomes lower than one (reaction-limited cluster-cluster aggregation). The analytical-ultracentrifugation data show that elevated temperatures induce dissociation of the dimeric Phb. The formation of a complex between the denatured monomeric form of Phb and the dissociated forms of GroEL is detected during heating at 46,C. [source]


Fluorescence-based soft-sensor for monitoring ,-lactoglobulin and ,-lactalbumin solubility during thermal aggregation

BIOTECHNOLOGY & BIOENGINEERING, Issue 3 2008
Rand Elshereef
Abstract A soft-sensor for monitoring solubility of native-like ,-lactalbumin (,-LA) and ,-lactoglobulin (,-LG) and their aggregation behavior following heat treatment of mixtures under different treatment conditions was developed using fluorescence spectroscopy data regressed with a multivariate Partial Least Squares (PLS) regression algorithm. PLS regression was used to correlate the concentrations of ,-LA and ,-LG to the fluorescence spectra obtained for their mixtures. Data for the calibration and validation of the soft sensor was derived from fluorescence spectra. The process of thermal induced aggregation of ,-LG and ,-LA protein in mixtures, which involves the disappearance of native-like proteins, was studied under various treatment conditions including different temperatures, pH, total initial protein concentration and proportions of ,-LA and ,-LG. It was demonstrated that the multivariate regression models used could effectively deconvolute multi-wavelength fluorescence spectra collected under a variety of process conditions and provide a fairly accurate quantification of respective native-like proteins despite the significant overlapping between their emission profiles. It was also demonstrated that a PLS model can be used as a black-box prediction tool for estimating protein aggregation when combined with simple mass balances. Bioeng. 2008;99: 567,577. 2007 Wiley Periodicals, Inc. [source]


Differences in the Effects of Solution Additives on Heat- and Refolding-Induced Aggregation

BIOTECHNOLOGY PROGRESS, Issue 2 2008
Hiroyuki Hamada
Although a number of low-molecular-weight additives have been developed to suppress protein aggregation, it is unclear whether these aggregation suppressors affect various aggregation processes in the same manner. In this study, we evaluated the differences in the effect of solution additives on heat- and refolding-induced aggregation in the presence of guanidine (Gdn), arginine (Arg), and spermidine (Spd), and the comparable analysis showed the following differences: (i) Gdn did not suppress thermal aggregation but increased the yield of oxidative refolding. (ii) Spd showed the highest effect for heat-induced aggregation suppression among tested compounds, although it promoted aggregation in oxidative refolding. (iii) Arg was effective for both aggregation processes. Lysozyme solubility assay and thermal unfolding experiment showed that Spd was preferentially excluded from native lysozyme and Arg and Gdn solubilized the model state of intermediates during oxidative refolding. This preference of additives to protein surfaces is the cause of the different effect on aggregation suppression. [source]