Automated NMR resonance assignments and structure determination using a minimal set of 4D spectra

Automated methods for NMR structure determination of proteins are continuously becoming more robust. However, current methods addressing larger, more complex targets rely on analyzing 6–10 complementary spectra, suggesting the need for alternative approaches. Here, we describe 4D-CHAINS/autoNOE-Rosetta, a complete pipeline for NOE-driven structure determination of medium- to larger-sized proteins. The 4D-CHAINS algorithm analyzes two 4D spectra recorded using a single, fully protonated protein sample in an iterative ansatz where common NOEs between different spin systems supplement conventional through-bond connectivities to establish assignments of sidechain and backbone resonances at high levels of completeness and with a minimum error rate. The 4D-CHAINS assignments are then used to guide automated assignment of long-range NOEs and structure refinement in autoNOE-Rosetta. Our results on four targets ranging in size from 15.5 to 27.3 kDa illustrate that the structures of proteins can be determined accurately and in an unsupervised manner in a matter of days

Analysis of the XPA and ssDNA-binding surfaces on the central domain of human ERCC1 reveals evidence for subfunctionalization.

Human ERCC1/XPF is a structure-specific endonuclease involved in multiple DNA repair pathways. We present the solution structure of the non-catalytic ERCC1 central domain. Although this domain shows structural homology with the catalytically active XPF nuclease domain, functional investigation reveals a completely distinct function for the ERCC1 central domain by performing interactions with both XPA and single-stranded DNA. These interactions are non-competitive and can occur simultaneously through distinct interaction surfaces. Interestingly, the XPA binding by ERCC1 and the catalytic function of XPF are dependent on a structurally homologous region of the two proteins. Although these regions are strictly conserved in each protein family, amino acid composition and surface characteristics are distinct. We discuss the possibility that after XPF gene duplication, the redundant ERCC1 central domain acquired novel functions, thereby increasing the fidelity of eukaryotic DNA repair

Distinct EH domains of the endocytic TPLATE complex confer lipid and protein binding

Clathrin-mediated endocytosis (CME) is the gatekeeper of the plasma membrane. In contrast to animals and yeasts, CME in plants depends on the TPLATE complex (TPC), an evolutionary ancient adaptor complex. However, the mechanistic contribution of the individual TPC subunits to plant CME remains elusive. In this study, we used a multidisciplinary approach to elucidate the structural and functional roles of the evolutionary conserved N-terminal Eps15 homology (EH) domains of the TPC subunit AtEH1/Pan1. By integrating high-resolution structural information obtained by X-ray crystallography and NMR spectroscopy with all-atom molecular dynamics simulations, we provide structural insight into the function of both EH domains. Both domains bind phosphatidic acid with a different strength, and only the second domain binds phosphatidylinositol 4,5-bisphosphate. Unbiased peptidome profiling by mass-spectrometry revealed that the first EH domain preferentially interacts with the double N-terminal NPF motif of a previously unidentified TPC interactor, the integral membrane protein Secretory Carrier Membrane Protein 5 (SCAMP5). Furthermore, we show that AtEH/Pan1 proteins control the internalization of SCAMP5 via this double NPF peptide interaction motif. Collectively, our structural and functional studies reveal distinct but complementary roles of the EH domains of AtEH/Pan1 in plant CME and connect the internalization of SCAMP5 to the TPLATE complex. AtEH/Pan1 proteins contain two N-terminal Eps15 homology (EH) domains and are subunits of the endocytic TPLATE complex present in plants. Here, the authors combine X-ray crystallography, NMR and MD simulations with biochemical and in planta analysis to characterize the two AtEH1/Pan1 EH domains and reveal their structural differences and complementary functional roles

Analysis of the XPA and ssDNA-binding surfaces

on the central domain of human ERCC1 reveals evidence for subfunctionalizatio

Structural and functional analysis of the DEAF-1 and BS69 MYND domains.

DEAF-1 is an important transcriptional regulator that is required for embryonic development and is linked to clinical depression and suicidal behavior in humans. It comprises various structural domains, including a SAND domain that mediates DNA binding and a MYND domain, a cysteine-rich module organized in a Cys(4)-Cys(2)-His-Cys (C4-C2HC) tandem zinc binding motif. DEAF-1 transcription regulation activity is mediated through interactions with cofactors such as NCoR and SMRT. Despite the important biological role of the DEAF-1 protein, little is known regarding the structure and binding properties of its MYND domain.Here, we report the solution structure, dynamics and ligand binding of the human DEAF-1 MYND domain encompassing residues 501-544 determined by NMR spectroscopy. The structure adopts a ββα fold that exhibits tandem zinc-binding sites with a cross-brace topology, similar to the MYND domains in AML1/ETO and other proteins. We show that the DEAF-1 MYND domain binds to peptides derived from SMRT and NCoR corepressors. The binding surface mapped by NMR titrations is similar to the one previously reported for AML1/ETO. The ligand binding and molecular functions of the related BS69 MYND domain were studied based on a homology model and mutational analysis. Interestingly, the interaction between BS69 and its binding partners (viral and cellular proteins) seems to require distinct charged residues flanking the predicted MYND domain fold, suggesting a different binding mode. Our findings demonstrate that the MYND domain is a conserved zinc binding fold that plays important roles in transcriptional regulation by mediating distinct molecular interactions with viral and cellular proteins

Studying Weak and Dynamic Interactions of Posttranslationally Modified Proteins using Expressed Protein Ligation

Many cellular processes are regulated by posttranslational modifications that are recognized by specific domains in protein binding partners. These interactions are often weak, thus allowing a highly dynamic and combinatorial regulatory network of protein–protein interactions. We report an efficient strategy that overcomes challenges in structural analysis of such a weak transient interaction between the Tudor domain of the Survival of Motor Neuron (SMN) protein and symmetrically dimethylated arginine (sDMA). The posttranslational modification is chemically introduced and covalently linked to the effector module by a one-pot expressed protein ligation (EPL) procedure also enabling segmental incorporation of NMR-active isotopes for structural analysis. Covalent coupling of the two interacting moieties shifts the equilibrium to the bound state, and stoichiometric interactions are formed even for low affinity interactions. Our approach should enable the structural analysis of weak interactions by NMR or X-ray crystallography to better understand the role of posttranslational modifications in dynamic biological processes

Automated NMR resonance assignments and structure determination using a minimal set of 4D spectra

Automated methods for NMR structure determination of proteins are continuously becoming more robust. However, current methods addressing larger, more complex targets rely on analyzing 6–10 complementary spectra, suggesting the need for alternative approaches. Here, we describe 4D-CHAINS/autoNOE-Rosetta, a complete pipeline for NOE-driven structure determination of medium- to larger-sized proteins. The 4D-CHAINS algorithm analyzes two 4D spectra recorded using a single, fully protonated protein sample in an iterative ansatz where common NOEs between different spin systems supplement conventional through-bond connectivities to establish assignments of sidechain and backbone resonances at high levels of completeness and with a minimum error rate. The 4D-CHAINS assignments are then used to guide automated assignment of long-range NOEs and structure refinement in autoNOE-Rosetta. Our results on four targets ranging in size from 15.5 to 27.3 kDa illustrate that the structures of proteins can be determined accurately and in an unsupervised manner in a matter of days.This article is published as Evangelidis, Thomas, Santrupti Nerli, Jiří Nováček, Andrew E. Brereton, P. Andrew Karplus, Rochelle R. Dotas, Vincenzo Venditti, Nikolaos G. Sgourakis, and Konstantinos Tripsianes. "Automated NMR resonance assignments and structure determination using a minimal set of 4D spectra." Nature Communications 9, no. 1 (2018): 384. DOI: 10.1038/s41467-017-02592-z. Posted with permission.</p

Binding of DEAF-1 MYND to SMRT and NCoR peptides.

<p>(a) Chemical Shift Perturbations (CSP, see methods) observed for the interaction between DEAF-1 MYND domain and SMRT (top) and NCoR (bottom) corepressor peptides. The sequence of SMRT and NCoR peptides used for the titrations are indicated in each graph. Secondary structure elements and amino acid sequence of the DEAF-1 MYND domain are shown at the top of the panel. Residues expected to interact with the corepressors are colored magenta. CSPs of residues that are most strongly affected are shown (cross symbols) as a function of ligand concentration for both titration with SMRT (top right) and NCoR (bottom right). The observed CSPs were fitted to a binding isotherm yielding dissociation constanst of 5.30±0.54 mM and 3.08±0.12 mM for the SMRT and NCoR peptides, respectively. The binding curves are shown as dashed lines. (b) Superposition of ¹H, ¹⁵N HSQC spectra of a 1 mM sample of the free DEAF-1 MYND domain (red) and upon addition of unlabeled corepressor peptides (cyan) up to a final concentration of 8 mM and 5 mM of SMRT and NCoR peptide (1∶8 and 1∶5 molar ratio), respectively. The intermediate steps of each titration are zoomed for a sub-region of the corresponding spectrum. In either case binding takes place on the fast exchange regime with respect to the chemical shift time scale. (c) Ribbon representation of DEAF-1 (left) and ETO (right) MYND domains. Residues experiencing the largest chemical shift perturbation upon addition of the corepressor peptides are shown as magenta sticks. In the ETO-SMRT complex structure the corresponding residues are shown as sticks as well, and the SMRT ligand peptide is colored orange and shown in cartoon representation.</p