scholarly journals The Role of Active Site Flexible Loops in Catalysis and of Zinc in Conformational Stability of Bacillus cereus 569/H/9 β-Lactamase

2016 ◽  
Vol 291 (31) ◽  
pp. 16124-16137 ◽  
Author(s):  
Caroline Montagner ◽  
Michaël Nigen ◽  
Olivier Jacquin ◽  
Nicolas Willet ◽  
Mireille Dumoulin ◽  
...  
Keyword(s):  
Bacillus Cereus ◽  
Active Site ◽  
Conformational Stability ◽  
Flexible Loops

scholarly journals Role of Disulfide Bridges in the Activity and Stability of a Cold-Active α-Amylase

2005 ◽  
Vol 187 (17) ◽  
pp. 6206-6212 ◽  
Author(s):  
Khawar Sohail Siddiqui ◽  
Anne Poljak ◽  
Michael Guilhaus ◽  
Georges Feller ◽  
Salvino D'Amico ◽  
...  
Keyword(s):  
Active Site ◽  
Disulfide Bonds ◽  
Conformational Stability ◽  
Iodoacetic Acid ◽  
Mass Spectrometry Analysis ◽  
Stable Region ◽  
Disulfide Bridges ◽  
Activity Increase ◽  
Spectrometry Analysis

ABSTRACT The cold-adapted α-amylase from Pseudoalteromonas haloplanktis unfolds reversibly and cooperatively according to a two-state mechanism at 30°C and unfolds reversibly and sequentially with two transitions at temperatures below 12°C. To examine the role of the four disulfide bridges in activity and conformational stability of the enzyme, the eight cysteine residues were reduced with β-mercaptoethanol or chemically modified using iodoacetamide or iodoacetic acid. Matrix-assisted laser desorption-time of flight mass spectrometry analysis confirmed that all of the cysteines were modified. The iodoacetamide-modified enzyme reversibly folded/unfolded and retained approximately one-third of its activity. Removal of all disulfide bonds resulted in stabilization of the least stable region of the enzyme (including the active site), with a concomitant decrease in activity (increase in activation enthalpy). Disulfide bond removal had a greater impact on enzyme activity than on stability (particularly the active-site region). The functional role of the disulfide bridges appears to be to prevent the active site from developing ionic interactions. Overall, the study demonstrated that none of the four disulfide bonds are important in stabilizing the native structure of enzyme, and instead, they appear to promote a localized destabilization to preserve activity.

scholarly journals Dual role of strigolactone receptor signaling partner in inhibiting substrate hydrolysis

2021 ◽  
Author(s):  
Briana L Sobecks ◽  
Jiming Chen ◽  
Diwakar Shukla
Keyword(s):  
Active Site ◽  
Conformational Stability ◽  
Critical Role ◽  
Md Simulations ◽  
Binding Pocket ◽  
Conformational Ensemble ◽  
Downstream Signaling ◽  
F Box Protein ◽  
Substrate Hydrolysis

Plant branch and root growth relies on metabolism of the strigolactone (SL) hormone. The interaction between the SL molecule, Oryza sativa DWARF14 (D14) SL receptor, and D3 F-box protein has been shown to play a critical role in SL perception. Previously, it was believed that D3 only interacts with the closed form of D14 to induce downstream signaling, but recent experiments indicate that D3, as well as its C-terminal helix (CTH), can interact with the open form as well to inhibit strigolactone signaling. Two hypotheses for the CTH induced inhibition are that either the CTH affects the conformational ensemble of D14 by stabilizing catalytically inactive states, or the CTH interacts with SLs in a way that prevents them from entering the binding pocket. In this study, we have performed molecular dynamics (MD) simulations to assess the validity of these hypotheses. We used an apo system with only D14 and the CTH to test the active site conformational stability and a holo system with D14, the CTH, and an SL molecule to test the interaction between the SL and CTH. Our simulations show that the CTH affects both active site conformation and the ability of SLs to move into the binding pocket. In the apo system, the CTH allosterically stabilized catalytic residues into their inactive conformation. In the holo system, significant interactions between SLs and the CTH hindered the ability of SLs to enter the D14 binding pocket. These two mechanisms account for the observed decrease in SL binding to D14 and subsequent ligand hydrolysis in the presence of the CTH.

scholarly journals Solution structures of the Bacillus cereus metallo-β-lactamase BcII and its complex with the broad spectrum inhibitor R-thiomandelic acid

2013 ◽  
Vol 456 (3) ◽  
pp. 397-407 ◽  
Author(s):  
Andreas Ioannis Karsisiotis ◽  
Christian F. Damblon ◽  
Gordon C. K. Roberts
Keyword(s):  
Antibiotic Resistance ◽  
Bacillus Cereus ◽  
Broad Spectrum ◽  
Active Site ◽  
Solution Structure ◽  
Inhibitor Binding ◽  
Solution Structures ◽  
Micro Organisms ◽  
Flexible Loops

Metallo-β-lactamases are important in antibiotic resistance in micro-organisms. We report the first solution structure of a metallo-β-lactamase and its complex with an inhibitor, allowing the key flexible loops flanking the active site and their role in inhibitor binding to be properly defined.

Role of ribosidase in germination of Bacillus cereus T spores induced.

1985 ◽  
Vol 40 (3) ◽  
pp. 581-587 ◽  
Author(s):  
Hirofumi SHIBATA ◽  
Noriaki OHNISHI ◽  
Keiko TAKEDA ◽  
Isamu TANI
Keyword(s):  
Bacillus Cereus

Exploring the Role of the Central Carbide of the Nitrogenase Active-Site FeMo-cofactor through Targeted 13C Labeling and ENDOR Spectroscopy

2021 ◽  
Author(s):  
Ana Pérez-González ◽  
Zhi-Yong Yang ◽  
Dmitriy A. Lukoyanov ◽  
Dennis R. Dean ◽  
Lance C. Seefeldt ◽  
...  
Keyword(s):  
Active Site ◽  
13C Labeling ◽  
Endor Spectroscopy ◽  
Femo Cofactor
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