scholarly journals Concerted dynamics between conserved histidines in the N-extein region regulates Mycobacterium tuberculosis SufB intein cleavage

2021 ◽  
Author(s):  
Sunita Panda ◽  
Ananya Nanda ◽  
Nilanjan Sahu ◽  
Deepak Kumar Ojha ◽  
Biswaranjan Pradhan ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Direct Interaction ◽  
Precursor Protein ◽  
Cluster Assembly ◽  
Cleavage Reaction ◽  
Functional Protein ◽  
Peptide Bonds ◽  
Dynamics Simulations ◽  
Distinct Features ◽  
Unique Mechanism

Inteins are auto-processing domains that implement a multi-step biochemical reaction termed protein splicing, marked by cleavage and formation of peptide bonds. They excise from a precursor protein, generating a functional protein via covalent bonding of flanking exteins. We report the kinetic study of splicing and cleavage reaction in a [Fe-S] cluster assembly protein SufB from Mycobacterium tuberculosis. Although it follows a canonical intein splicing pathway, distinct features are added by extein residues present in the active site. Sequence analysis identified two conserved histidines in the N-extein region; His-5 and His-38. Kinetic analyses of His-5Ala and His-38Ala SufB mutants exhibited significant reductions in splicing and cleavage rates relative to the SufB wild-type precursor protein. Structural analysis and molecular dynamics simulations suggested that Mtu SufB displays a unique mechanism where two remote histidines work concurrently to facilitate N- cleavage reaction. His-5, which is exposed outside, because of the random push of water molecules forces His-38 towards the N-cleavage site. Thus, His-5 stabilizes the position of His-38 which in turn activates N-S acyl shift via direct interaction with catalytic Cys1. Understanding intein~extein partnership in an essential mycobacterial protein may diversify into intein-based applied research along with the development of pathogen-specific novel antimicrobials.

scholarly journals “Newton’s cradle” proton relay with amide–imidic acid tautomerization in inverting cellulase visualized by neutron crystallography

2015 ◽  
Vol 1 (7) ◽  
pp. e1500263 ◽  
Author(s):  
Akihiko Nakamura ◽  
Takuya Ishida ◽  
Katsuhiro Kusaka ◽  
Taro Yamada ◽  
Shinya Fushinobu ◽  
...  
Keyword(s):  
Glycoside Hydrolases ◽  
Side Chain ◽  
Enzymatic Reactions ◽  
X Ray Diffraction ◽  
Peptide Bonds ◽  
Proton Relay ◽  
Newton’S Cradle ◽  
Dynamics Simulations ◽  
Hydrolysis Of

Hydrolysis of carbohydrates is a major bioreaction in nature, catalyzed by glycoside hydrolases (GHs). We used neutron diffraction and high-resolution x-ray diffraction analyses to investigate the hydrogen bond network in inverting cellulase PcCel45A, which is an endoglucanase belonging to subfamily C of GH family 45, isolated from the basidiomycete Phanerochaete chrysosporium. Examination of the enzyme and enzyme-ligand structures indicates a key role of multiple tautomerizations of asparagine residues and peptide bonds, which are finally connected to the other catalytic residue via typical side-chain hydrogen bonds, in forming the “Newton’s cradle”–like proton relay pathway of the catalytic cycle. Amide–imidic acid tautomerization of asparagine has not been taken into account in recent molecular dynamics simulations of not only cellulases but also general enzyme catalysis, and it may be necessary to reconsider our interpretation of many enzymatic reactions.

scholarly journals Elucidating the structural features of ABCA1 in its heterogeneous membrane environment.

2021 ◽  
Author(s):  
Sunidhi S ◽  
Sukriti Sacher ◽  
Parth Garg ◽  
Arjun Ray
Keyword(s):  
Conformational Changes ◽  
Transmembrane Protein ◽  
Direct Interaction ◽  
Structural Features ◽  
Lipid Binding ◽  
Lipid Monolayer ◽  
Alternative Theory ◽  
Lipid Dynamics ◽  
Lipid Environment ◽  
Dynamics Simulations

ABCA1 plays an integral part in Reverse Cholesterol Transport (RCT) and is critical for maintaining lipid homeostasis. One theory of lipid efflux by the transporter (alternating access) proposes that ABCA1 harbors two different conformations that provide alternate access for lipid binding and release, leading to sequestration via a direct interaction between ABCA1 and its partner, ApoA1. The alternative theory (lateral access) proposes that ABCA1 obtains lipids laterally from the membrane to form a temporary extracellular reservoir containing an isolated pressurized lipid monolayer caused by the net accumulation of lipids in the exofacial leaflet. Recently, a full-length Cryo-EM structure of this 2,261-residue transmembrane protein showed its discreetly folded domains and conformations, as well as detected the presence of a tunnel enclosed within ECDs. While the tunnel was wide enough at the proximal end for accommodating passage of lipids, the distal end displayed substantial narrowing, making it inaccessible for ApoA1. Therefore, this structure was hypothesized to substantiate the lateral access theory, whereby ApoA1 obtained lipids from the proximal end. Utilizing long time-scale multiple replica atomistic molecular dynamics simulations (MDS), we simulated the structure in a heterogeneous lipid environment and found that along with several large conformational changes, the protein widens enough at the distal end of its ECD tunnel to now enable lipid accommodation. In this study we have characterized ABCA1 and the lipid dynamics along with the protein-lipid interactions in the heterogeneous environment, providing novel insights into understanding ABCA1 conformation at an atomistic level.

scholarly journals Small RNA profiling in Mycobacterium tuberculosis identifies MrsI as necessary for an anticipatory iron sparing response

2018 ◽  
Vol 115 (25) ◽  
pp. 6464-6469 ◽  
Author(s):  
Elias R. Gerrick ◽  
Thibault Barbier ◽  
Michael R. Chase ◽  
Raylin Xu ◽  
Josie François ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Large Scale ◽  
Direct Interaction ◽  
Human Macrophage ◽  
Binding Interaction ◽  
Bacterial Gene ◽  
Rna Profiling ◽  
Iron Deprivation ◽  
Bacterial Gene Expression ◽  
Small Regulatory Rnas

One key to the success of Mycobacterium tuberculosis as a pathogen is its ability to reside in the hostile environment of the human macrophage. Bacteria adapt to stress through a variety of mechanisms, including the use of small regulatory RNAs (sRNAs), which posttranscriptionally regulate bacterial gene expression. However, very little is currently known about mycobacterial sRNA-mediated riboregulation. To date, mycobacterial sRNA discovery has been performed primarily in log-phase growth, and no direct interaction between any mycobacterial sRNA and its targets has been validated. Here, we performed large-scale sRNA discovery and expression profiling in M. tuberculosis during exposure to five pathogenically relevant stresses. From these data, we identified a subset of sRNAs that are highly induced in multiple stress conditions. We focused on one of these sRNAs, ncRv11846, here renamed mycobacterial regulatory sRNA in iron (MrsI). We characterized the regulon of MrsI and showed in mycobacteria that it regulates one of its targets, bfrA, through a direct binding interaction. MrsI mediates an iron-sparing response that is required for optimal survival of M. tuberculosis under iron-limiting conditions. However, MrsI is induced by multiple host-like stressors, which appear to trigger MrsI as part of an anticipatory response to impending iron deprivation in the macrophage environment.

Solvation chemical shifts of perylenic antenna molecules from molecular dynamics simulations

2014 ◽  
Vol 16 (40) ◽  
pp. 22309-22320 ◽  
Author(s):  
Nergiz Özcan ◽  
Jiří Mareš ◽  
Dage Sundholm ◽  
Juha Vaara
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Chemical Shifts ◽  
Solvation Model ◽  
Nmr Chemical Shifts ◽  
Dynamics Simulations ◽  
Distinct Features

Solvent-induced carbon-13 NMR chemical shifts of nine candidate antenna molecules were analysed using a dynamic solvation model, revealing the distinct features of perimeter and inside nuclear sites.

scholarly journals Altered Integration of Matrilin-3 into Cartilage Extracellular Matrix in the Absence of Collagen IX

2005 ◽  
Vol 25 (23) ◽  
pp. 10465-10478 ◽  
Author(s):  
Bastian Budde ◽  
Katrin Blumbach ◽  
Joni Ylöstalo ◽  
Frank Zaucke ◽  
Harald W. A. Ehlen ◽  
...  
Keyword(s):  
Extracellular Matrix ◽  
Knockout Mice ◽  
Matrix Protein ◽  
Protein Extraction ◽  
Direct Interaction ◽  
Matrix Proteins ◽  
Functional Protein ◽  
Cartilage Extracellular Matrix ◽  
Vertebral Bodies ◽  
Collagen Ix

ABSTRACT The matrilins are a family of four noncollagenous oligomeric extracellular matrix proteins with a modular structure. Matrilins can act as adapters which bridge different macromolecular networks. We therefore investigated the effect of collagen IX deficiency on matrilin-3 integration into cartilage tissues. Mice harboring a deleted Col9a1 gene lack synthesis of a functional protein and produce cartilage fibrils completely devoid of collagen IX. Newborn collagen IX knockout mice exhibited significantly decreased matrilin-3 and cartilage oligomeric matrix protein (COMP) signals, particularly in the cartilage primordium of vertebral bodies and ribs. In the absence of collagen IX, a substantial amount of matrilin-3 is released into the medium of cultured chondrocytes instead of being integrated into the cell layer as in wild-type and COMP-deficient cells. Gene expression of matrilin-3 is not affected in the absence of collagen IX, but protein extraction from cartilage is greatly facilitated. Matrilin-3 interacts with collagen IX-containing cartilage fibrils, while fibrils from collagen IX knockout mice lack matrilin-3, and COMP-deficient fibrils exhibit an intermediate integration. In summary, the integration of matrilin-3 into cartilage fibrils occurs both by a direct interaction with collagen IX and indirectly with COMP serving as an adapter. Matrilin-3 can be considered as an interface component, capable of interconnecting macromolecular networks and mediating interactions between cartilage fibrils and the extrafibrillar matrix.

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