Equilibrium unfolding studies of barstar: Evidence for an alternative conformation which resembles a molten globule

Biochemistry ◽  
1994 ◽  
Vol 33 (1) ◽  
pp. 106-115 ◽  
Author(s):  
Ritu Khurana ◽  
Jayant B. Udgaonkar
Keyword(s):  
Molten Globule ◽  
Alternative Conformation ◽  
Equilibrium Unfolding

Probing the Acid-Induced Packing Structure Changes of the Molten Globule Domains of a Protein near Equilibrium Unfolding

2017 ◽  
Vol 8 (2) ◽  
pp. 470-477 ◽  
Author(s):  
Yi-Qi Yeh ◽  
Kuei-Fen Liao ◽  
Orion Shih ◽  
Ying-Jen Shiu ◽  
Wei-Ru Wu ◽  
...  
Keyword(s):  
Molten Globule ◽  
Packing Structure ◽  
Structure Changes ◽  
Equilibrium Unfolding

Denaturant Induced Equilibrium Unfolding and Conformational Transitional Studies of Germinated Fenugreek β-Amylase Revealed Molten Globule like State at Low pH

2020 ◽  
Vol 27 (10) ◽  
pp. 1046-1057
Author(s):  
Dinesh Chand Agrawal ◽  
Anjali Yadav ◽  
Mohd. Asim Khan ◽  
Suman Kundu ◽  
Arvind M. Kayastha
Keyword(s):  
Circular Dichroism ◽  
Catalytic Domain ◽  
Molten Globule ◽  
Intrinsic Fluorescence ◽  
Tertiary Structures ◽  
Near Ultraviolet ◽  
Equilibrium Unfolding ◽  
Α Helix ◽  
Far Ultraviolet ◽  
Circular Dichroïsm

Background: β-Amylase (EC 3.2.1.2) is a maltogenic enzyme, which releases β-maltose from the non-reducing end of the substrates. The enzyme plays important roles for the production of vaccine, maltiol and maltose rich syrups. Apart from these applications the enzyme protects cells from abiotic as well as oxidative damage. The enzyme is βwell characterized in βplants and microbes and crystal structures of β-amylases βhave been βobtained from sweet potato, soybean and Bacillus cereus. Objective: Find out correlation between structural and functional stability induced by change in pH, temperature and chaotropes. Methods: Activity, intrinsic fluorescence, extrinsic fluorescence, near- and far- ultraviolet circular dichroism spectroscopic measurements were performed. Results: Peaks about 208 nm and 222 nm obtained by near-ultraviolet circular dichroism correspond to α-helix whereas peak at 215 nm shows presence of β-sheet. At pH 2.0, absence of tertiary structures, exposed of hydrophobic regions and presence of substantial secondary structures, revealed the existence of molten globule like state. Temperature induced denaturation studies showed that the enzyme was stable up to 75 ºC and the process was found to be irreversible in nature. Chaotropes dependent equilibrium unfolding studies revealed that at low concentration of chaotropes, ellipticity and intrinsic fluorescence βintensity were βdecreased βwhereas βenzymatic activity remained unchanged, which revealed fenugreek β-amylase is multi-domains enzyme and catalytic βdomain βis more βstable compare to non-catalytic domain. Moreover, the transition was sigmoidal and non-coincidental. Conclusion: Results indicate the probable existence of intermediate states that might perform significant role in physiological process and biotechnological applications.

scholarly journals Folding mechanism of canine milk lysozyme studied by circular dichroism and fluorescence spectroscopy

2003 ◽  
Vol 17 (2-3) ◽  
pp. 183-193 ◽  
Author(s):  
Masaharu Nakao ◽  
Munehito Arai ◽  
Takumi Koshiba ◽  
Katsutoshi Nitta ◽  
Kunihiro Kuwajima
Keyword(s):  
Circular Dichroism ◽  
Fluorescence Spectroscopy ◽  
Molten Globule ◽  
Guanidine Hydrochloride ◽  
Folding Intermediates ◽  
Equilibrium Unfolding ◽  
Burst Phase ◽  
The Relationship ◽  
Kinetics Of ◽  
Circular Dichroïsm

We have studied the guanidine hydrochloride‒induced equilibrium unfolding and the kinetics of refolding of canine milk lysozyme by circular dichroism and fluorescence spectroscopy. The thermodynamic analysis of the equilibrium unfolding measured by circular dichroism and fluorescence has shown that unfolding is represented by a three‒state mechanism and that the intermediate state of canine milk lysozyme is remarkably more stable than the intermediates observed in other lysozyme and α-lactalbumin. In the kinetic refolding of this protein, there are at least two kinetic intermediates; a burst=phase intermediate accumulated within the dead time (4 ms) of the measurement and an intermediate that has been observed during the kinetics with a rate constant of 10–20 s–1after the burst phase. This result is apparently in contrast with those previously observed in the kinetic refolding of α‒lactalbumin and equine lysozyme that show only the burst‒phase intermediate. The relationship between the extraordinarily stable equilibrium molten globule and the kinetic folding intermediates will be discussed.

scholarly journals Predissociated Dimers and Molten Globule Monomers in the Equilibrium Unfolding of Yeast Glutathione Reductase

2003 ◽  
Vol 85 (5) ◽  
pp. 3255-3261 ◽  
Author(s):  
Paulo Roberto Louzada ◽  
Adriano Sebollela ◽  
Marcelo E. Scaramello ◽  
Sérgio T. Ferreira
Keyword(s):  
Glutathione Reductase ◽  
Molten Globule ◽  
Equilibrium Unfolding

Stability and Folding of the Unusually Stable Hemoglobin from Synechocystis is Subtly Optimized and Dependent on the Key Heme Pocket Residues.

2020 ◽  
Vol 27 ◽  
Author(s):  
Sheetal Uppal ◽  
Mohd. Asim Khan ◽  
Suman Kundu
Keyword(s):  
Molten Globule ◽  
Life Forms ◽  
Model System ◽  
Heme Pocket ◽  
The Past ◽  
Specific Manner ◽  
Delivery Vehicles ◽  
The Stability ◽  
Key Residues ◽  
Synechocystis Sp

Aims: The aim of our study is to understand the biophysical traits that govern the stability and folding of Synechocystis hemoglobin, a unique cyanobacterial globin that displays unusual traits not observed in any of the other globins discovered so far. Background: For the past few decades, classical hemoglobins such as vertebrate hemoglobin and myoglobin have been extensively studied to unravel the stability and folding mechanisms of hemoglobins. However, the expanding wealth of hemoglobins identified in all life forms with novel properties, like heme coordination chemistry and globin fold, have added complexity and challenges to the understanding of hemoglobin stability, which has not been adequately addressed. Here, we explored the unique truncated and hexacoordinate hemoglobin from the freshwater cyanobacterium Synechocystis sp. PCC 6803 known as “Synechocystis hemoglobin (SynHb)”. The “three histidines” linkages to heme are novel to this cyanobacterial hemoglobin. Objective: Mutational studies were employed to decipher the residues within the heme pocket that dictate the stability and folding of SynHb. Methods: Site-directed mutants of SynHb were generated and analyzed using a repertoire of spectroscopic and calorimetric tools. Result: The results revealed that the heme was stably associated to the protein under all denaturing conditions with His117 playing the anchoring role. The studies also highlighted the possibility of existence of a “molten globule” like intermediate at acidic pH in this exceptionally thermostable globin. His117 and other key residues in the heme pocket play an indispensable role in imparting significant polypeptide stability. Conclusion: Synechocystis hemoglobin presents an important model system for investigations of protein folding and stability in general. The heme pocket residues influenced the folding and stability of SynHb in a very subtle and specific manner and may have been optimized to make this Hb the most stable known as of date. Other: The knowledge gained hereby about the influence of heme pocket amino acid side chains on stability and expression is currently being utilized to improve the stability of recombinant human Hbs for efficient use as oxygen delivery vehicles.

Unfolding of the molten globule state of .alpha.-lactalbumin studied by proton NMR

Biochemistry ◽  
1993 ◽  
Vol 32 (48) ◽  
pp. 13198-13203 ◽  
Author(s):  
Akio Shimizu ◽  
Masamichi Ikeguchi ◽  
Shintaro Sugai
Keyword(s):  
Molten Globule ◽  
Proton Nmr ◽  
Molten Globule State ◽  
Alpha Lactalbumin
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