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20 pages, 4293 KiB

Open AccessArticle

Dynamics-Derived Insights into Complex Formation between the CXCL8 Monomer and CXCR1 N-Terminal Domain: An NMR Study

by Prem Raj B. Joseph, Leo Spyracopoulos and Krishna Rajarathnam

Molecules 2018, 23(11), 2825; https://doi.org/10.3390/molecules23112825 - 31 Oct 2018

Cited by 5 | Viewed by 3278

Abstract

Interleukin-8 (CXCL8), a potent neutrophil-activating chemokine, exerts its function by activating the CXCR1 receptor that belongs to class A G protein-coupled receptors (GPCRs). Receptor activation involves interactions between the CXCL8 N-terminal loop and CXCR1 N-terminal domain (N-domain) residues (Site-I) and between the CXCL8 [...] Read more.

Interleukin-8 (CXCL8), a potent neutrophil-activating chemokine, exerts its function by activating the CXCR1 receptor that belongs to class A G protein-coupled receptors (GPCRs). Receptor activation involves interactions between the CXCL8 N-terminal loop and CXCR1 N-terminal domain (N-domain) residues (Site-I) and between the CXCL8 N-terminal and CXCR1 extracellular/transmembrane residues (Site-II). CXCL8 exists in equilibrium between monomers and dimers, and it is known that the monomer binds CXCR1 with much higher affinity and that Site-I interactions are largely responsible for the differences in monomer vs. dimer affinity. Here, using backbone ¹⁵N-relaxation nuclear magnetic resonance (NMR) data, we characterized the dynamic properties of the CXCL8 monomer and the CXCR1 N-domain in the free and bound states. The main chain of CXCL8 appears largely rigid on the picosecond time scale as evident from high order parameters (S²). However, on average, S² are higher in the bound state. Interestingly, several residues show millisecond-microsecond (ms-μs) dynamics only in the bound state. The CXCR1 N-domain is unstructured in the free state but structured with significant dynamics in the bound state. Isothermal titration calorimetry (ITC) data indicate that both enthalpic and entropic factors contribute to affinity, suggesting that increased slow dynamics in the bound state contribute to affinity. In sum, our data indicate a critical and complex role for dynamics in driving CXCL8 monomer-CXCR1 Site-I interactions. Full article

(This article belongs to the Special Issue NMR as a Tool to Investigate Biomolecular Structure, Recognition and Dynamics)

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12 pages, 3642 KiB

Open AccessArticle

Structural Basis for the Interaction between p53 Transactivation Domain and the Mediator Subunit MED25

by Min-Sung Lee, Kyungeun Lim, Mi-Kyung Lee and Seung-Wook Chi

Molecules 2018, 23(10), 2726; https://doi.org/10.3390/molecules23102726 - 22 Oct 2018

Cited by 10 | Viewed by 4375

Abstract

Eukaryotic transcription initiation is mediated by interactions between transcriptional activators and the mediator coactivator complex. Molecular interaction of p53 transcription factor with mediator complex subunit 25 (MED25) is essential for its target gene transcription. In this study, we characterized the molecular interaction between [...] Read more.

Eukaryotic transcription initiation is mediated by interactions between transcriptional activators and the mediator coactivator complex. Molecular interaction of p53 transcription factor with mediator complex subunit 25 (MED25) is essential for its target gene transcription. In this study, we characterized the molecular interaction between p53 transactivation domain (p53TAD) and activator interaction domain (ACID) of MED25 using nuclear magnetic resonance (NMR) spectroscopy. The NMR chemical shift perturbation and isothermal titration calorimetry (ITC) data showed that p53TAD interacted with MED25 ACID mainly through the p53TAD2 sequence motif. Taken together with the mutagenesis data, the refined structural model of MED25 ACID/p53TAD2 peptide complex showed that an amphipathic α-helix of p53TAD2 peptide bound an elongated hydrophobic groove of MED25 ACID. Furthermore, our results revealed the highly conserved mechanism of MED25 interaction with intrinsically unfolded acidic TADs from the transcriptional activators p53, ERM (Ets-related molecule), and herpes simplex virus protein 16 (VP16). Full article

(This article belongs to the Special Issue NMR as a Tool to Investigate Biomolecular Structure, Recognition and Dynamics)

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15 pages, 9145 KiB

Open AccessArticle

Multimodal Ligand Binding Studies of Human and Mouse G-Coupled Taste Receptors to Correlate Their Species-Specific Sweetness Tasting Properties

by Fariba M. Assadi-Porter, James Radek, Hongyu Rao and Marco Tonelli

Molecules 2018, 23(10), 2531; https://doi.org/10.3390/molecules23102531 - 03 Oct 2018

Cited by 9 | Viewed by 6825

Abstract

Taste signaling is a complex process that is linked to obesity and its associated metabolic syndromes. The sweet taste is mediated through a heterodimeric G protein coupled receptor (GPCR) in a species-specific manner and at multi-tissue specific levels. The sweet receptor recognizes a [...] Read more.

Taste signaling is a complex process that is linked to obesity and its associated metabolic syndromes. The sweet taste is mediated through a heterodimeric G protein coupled receptor (GPCR) in a species-specific manner and at multi-tissue specific levels. The sweet receptor recognizes a large number of ligands with structural and functional diversities to modulate different amplitudes of downstream signaling pathway(s). The human sweet-taste receptor has been extremely difficult to study by biophysical methods due to the difficulty in producing large homogeneous quantities of the taste-receptor protein and the lack of reliable in vitro assays to precisely measure productive ligand binding modes that lead to activation of the receptor protein. We report here a multimodal high throughput assay to monitor ligand binding, receptor stability and conformational changes to model the molecular ligand-receptor interactions. We applied saturation transfer difference nuclear magnetic resonance spectroscopy (STD-NMR) complemented by differential scanning calorimetry (DSC), circular dichroism (CD) spectroscopy, and intrinsic fluorescence spectroscopy (IF) to characterize binding interactions. Our method using complementary NMR and biophysical analysis is advantageous to study the mechanism of ligand binding and signaling processes in other GPCRs. Full article

(This article belongs to the Special Issue NMR as a Tool to Investigate Biomolecular Structure, Recognition and Dynamics)

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15 pages, 3245 KiB

Open AccessArticle

Spatial Overlap of Claudin- and Phosphatidylinositol Phosphate-Binding Sites on the First PDZ Domain of Zonula Occludens 1 Studied by NMR

by Hidekazu Hiroaki, Kaori Satomura, Natsuko Goda, Yukako Nakakura, Minami Hiranuma, Takeshi Tenno, Daizo Hamada and Takahisa Ikegami

Molecules 2018, 23(10), 2465; https://doi.org/10.3390/molecules23102465 - 26 Sep 2018

Cited by 7 | Viewed by 5255

Abstract

Background: The tight junction is an intercellular adhesion complex composed of claudins (CLDs), occludin, and the scaffolding proteins zonula occludens 1 (ZO-1) and its two paralogs ZO-2 and ZO-3. ZO-1 is a multifunctional protein that contains three PSD95/Discs large/ZO-1(PDZ) domains. A key [...] Read more.

Background: The tight junction is an intercellular adhesion complex composed of claudins (CLDs), occludin, and the scaffolding proteins zonula occludens 1 (ZO-1) and its two paralogs ZO-2 and ZO-3. ZO-1 is a multifunctional protein that contains three PSD95/Discs large/ZO-1(PDZ) domains. A key functional domain of ZO-1 is the first PDZ domain (ZO-1(PDZ1)) that recognizes the conserved C-termini of CLDs. Methods: In this study, we confirmed that phosphoinositides bound directly to ZO-1(PDZ1) by biochemical and solution NMR experiments. We further determined the solution structure of mouse ZO-1(PDZ1) by NMR and mapped the phosphoinositide binding site onto its molecular surface. Results: The phosphoinositide binding site was spatially overlapped with the CLD-binding site of ZO-1(PDZ1). Accordingly, inositol-hexaphosphate (phytic acid), an analog of the phosphoinositide head group, competed with ZO-1(PDZ)-CLD interaction. Conclusions: The results suggested that the PDZ domain–phosphoinositide interaction plays a regulatory role in biogenesis and homeostasis of the tight junction. Full article

(This article belongs to the Special Issue NMR as a Tool to Investigate Biomolecular Structure, Recognition and Dynamics)

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21 pages, 3568 KiB

Open AccessArticle

Substrate Binding Switches the Conformation at the Lynchpin Site in the Substrate-Binding Domain of Human Hsp70 to Enable Allosteric Interdomain Communication

by Kohei Umehara, Miho Hoshikawa, Naoya Tochio and Shin-ichi Tate

Molecules 2018, 23(3), 528; https://doi.org/10.3390/molecules23030528 - 27 Feb 2018

Cited by 10 | Viewed by 3974

Abstract

The stress-induced 70 kDa heat shock protein (Hsp70) functions as a molecular chaperone to maintain protein homeostasis. Hsp70 contains an N-terminal ATPase domain (NBD) and a C-terminal substrate-binding domain (SBD). The SBD is divided into the β subdomain containing the substrate-binding site (βSBD) [...] Read more.

The stress-induced 70 kDa heat shock protein (Hsp70) functions as a molecular chaperone to maintain protein homeostasis. Hsp70 contains an N-terminal ATPase domain (NBD) and a C-terminal substrate-binding domain (SBD). The SBD is divided into the β subdomain containing the substrate-binding site (βSBD) and the α-helical subdomain (αLid) that covers the βSBD. In this report, the solution structures of two different forms of the SBD from human Hsp70 were solved. One structure shows the αLid bound to the substrate-binding site intramolecularly, whereas this intramolecular binding mode is absent in the other structure solved. Structural comparison of the two SBDs from Hsp70 revealed that client-peptide binding rearranges residues at the interdomain contact site, which impairs interdomain contact between the SBD and the NBD. Peptide binding also disrupted the inter-subdomain interaction connecting the αLid to the βSBD, which allows the binding of the αLid to the NBD. The results provide a mechanism for interdomain communication upon substrate binding from the SBD to the NBD via the lynchpin site in the βSBD of human Hsp70. In comparison to the bacterial ortholog, DnaK, some remarkable differences in the allosteric signal propagation among residues within the Hsp70 SBD exist. Full article

(This article belongs to the Special Issue NMR as a Tool to Investigate Biomolecular Structure, Recognition and Dynamics)

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Review

Jump to: Research

25 pages, 4656 KiB

Open AccessReview

Glycosaminoglycan-Protein Interactions by Nuclear Magnetic Resonance (NMR) Spectroscopy

by Vitor H. Pomin and Xu Wang

Molecules 2018, 23(9), 2314; https://doi.org/10.3390/molecules23092314 - 11 Sep 2018

Cited by 11 | Viewed by 6559

Abstract

Nuclear magnetic resonance (NMR) spectroscopy is one of the most utilized and informative analytical techniques for investigating glycosaminoglycan (GAG)-protein complexes. NMR methods that are commonly applied to GAG-protein systems include chemical shift perturbation, saturation transfer difference, and transferred nuclear Overhauser effect. Although these [...] Read more.

Nuclear magnetic resonance (NMR) spectroscopy is one of the most utilized and informative analytical techniques for investigating glycosaminoglycan (GAG)-protein complexes. NMR methods that are commonly applied to GAG-protein systems include chemical shift perturbation, saturation transfer difference, and transferred nuclear Overhauser effect. Although these NMR methods have revealed valuable insight into the protein-GAG complexes, elucidating high-resolution structural and dynamic information of these often transient interactions remains challenging. In addition, preparation of structurally homogeneous and isotopically enriched GAG ligands for structural investigations continues to be laborious. As a result, understanding of the structure-activity relationship of GAGs is still primitive. To overcome these deficiencies, several innovative NMR techniques have been developed lately. Here, we review some of the commonly used techniques along with more novel methods such as waterLOGSY and experiments to examine structure and dynamic of lysine and arginine side chains to identify GAG-binding sites. We will also present the latest technology that is used to produce isotopically enriched as well as paramagnetically tagged GAG ligands. Recent results that were obtained from solid-state NMR of amyloid’s interaction with GAG are also presented together with a brief discussion on computer assisted modeling of GAG-protein complexes using sparse experimental data. Full article

(This article belongs to the Special Issue NMR as a Tool to Investigate Biomolecular Structure, Recognition and Dynamics)

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34 pages, 4069 KiB

Open AccessReview

NMR as a Tool to Investigate the Processes of Mitochondrial and Cytosolic Iron-Sulfur Cluster Biosynthesis

by Kai Cai and John L. Markley

Molecules 2018, 23(9), 2213; https://doi.org/10.3390/molecules23092213 - 31 Aug 2018

Cited by 9 | Viewed by 6360

Abstract

Iron-sulfur (Fe-S) clusters, the ubiquitous protein cofactors found in all kingdoms of life, perform a myriad of functions including nitrogen fixation, ribosome assembly, DNA repair, mitochondrial respiration, and metabolite catabolism. The biogenesis of Fe-S clusters is a multi-step process that involves the participation [...] Read more.

Iron-sulfur (Fe-S) clusters, the ubiquitous protein cofactors found in all kingdoms of life, perform a myriad of functions including nitrogen fixation, ribosome assembly, DNA repair, mitochondrial respiration, and metabolite catabolism. The biogenesis of Fe-S clusters is a multi-step process that involves the participation of many protein partners. Recent biophysical studies, involving X-ray crystallography, nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry (MS), and small angle X-ray scattering (SAXS), have greatly improved our understanding of these steps. In this review, after describing the biological importance of iron sulfur proteins, we focus on the contributions of NMR spectroscopy has made to our understanding of the structures, dynamics, and interactions of proteins involved in the biosynthesis of Fe-S cluster proteins. Full article

(This article belongs to the Special Issue NMR as a Tool to Investigate Biomolecular Structure, Recognition and Dynamics)

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14 pages, 3186 KiB

Open AccessReview

A Dynamic Overview of Antimicrobial Peptides and Their Complexes

by Viviane Silva De Paula and Ana Paula Valente

Molecules 2018, 23(8), 2040; https://doi.org/10.3390/molecules23082040 - 15 Aug 2018

Cited by 17 | Viewed by 4058

Abstract

In this narrative review, we comprehensively review the available information about the recognition, structure, and dynamics of antimicrobial peptides (AMPs). Their complex behaviors occur across a wide range of time scales and have been challenging to portray. Recent advances in nuclear magnetic resonance [...] Read more.

In this narrative review, we comprehensively review the available information about the recognition, structure, and dynamics of antimicrobial peptides (AMPs). Their complex behaviors occur across a wide range of time scales and have been challenging to portray. Recent advances in nuclear magnetic resonance and molecular dynamics simulations have revealed the importance of the molecular plasticity of AMPs and their abilities to recognize targets. We also highlight experimental data obtained using nuclear magnetic resonance methodologies, showing that conformational selection is a major mechanism of target interaction in AMP families. Full article

(This article belongs to the Special Issue NMR as a Tool to Investigate Biomolecular Structure, Recognition and Dynamics)

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12 pages, 2632 KiB

Open AccessFeature PaperReview

Probing Protein-Protein Interactions Using Asymmetric Labeling and Carbonyl-Carbon Selective Heteronuclear NMR Spectroscopy

by Erik K. Larsen, Cristina Olivieri, Caitlin Walker, Manu V.S., Jiali Gao, David A. Bernlohr, Marco Tonelli, John L. Markley and Gianluigi Veglia

Molecules 2018, 23(8), 1937; https://doi.org/10.3390/molecules23081937 - 03 Aug 2018

Cited by 9 | Viewed by 4764

Abstract

Protein-protein interactions (PPIs) regulate a plethora of cellular processes and NMR spectroscopy has been a leading technique for characterizing them at the atomic resolution. Technically, however, PPIs characterization has been challenging due to multiple samples required to characterize the hot spots at the [...] Read more.

Protein-protein interactions (PPIs) regulate a plethora of cellular processes and NMR spectroscopy has been a leading technique for characterizing them at the atomic resolution. Technically, however, PPIs characterization has been challenging due to multiple samples required to characterize the hot spots at the protein interface. In this paper, we review our recently developed methods that greatly simplify PPI studies, which minimize the number of samples required to fully characterize residues involved in the protein-protein binding interface. This original strategy combines asymmetric labeling of two binding partners and the carbonyl-carbon label selective (CCLS) pulse sequence element implemented into the heteronuclear single quantum correlation (¹H-¹⁵N HSQC) spectra. The CCLS scheme removes signals of the J-coupled ¹⁵N–¹³C resonances and records simultaneously two individual amide fingerprints for each binding partner. We show the application to the measurements of chemical shift correlations, residual dipolar couplings (RDCs), and paramagnetic relaxation enhancements (PRE). These experiments open an avenue for further modifications of existing experiments facilitating the NMR analysis of PPIs. Full article

(This article belongs to the Special Issue NMR as a Tool to Investigate Biomolecular Structure, Recognition and Dynamics)

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