Biology subjects

Destan, E.

Publications and source records attributed to Destan, E..

12 recordsLinked to original sources

bioRxiv2025

Deciphering the altered conformational states of bifunctional thaumarchaeal crotonyl-CoA hydratase and 3-hydroxypropionyl-CoA dehydratase from Nitrosopumilus maritimus

The thaumarchaeal 3-hydroxypropionate/4-hydroxybutyrate (3HP/4HB) cycle represents one of the most efficient mechanisms for CO2 fixation discovered to date. Within this cycle, the enzyme encoded by Nmar_1308 from Nitrosopumilus maritimus SCM1 plays a crucial role due to its dual functionality as both a crotonyl-CoA hydratase (CCAH) and a 3-hydroxypropionyl-CoA dehydratase (3HPD). Although the importance of a bifunctional enzyme for lowering the cost of biosynthesis, the details of structural dynamics are still missing. Here, in addition to our cryogenic temperature structures, we determined the first ambient temperature structures of the Nmar_1308 protein by Serial Femtosecond X-ray Crystallography (SFX). The determined structures capture previously unobserved conformational dynamics of the Nmar_1308 protein, providing invaluable information for future synthetic biology applications.

biochemistry↗

bioRxiv2024

Experimental and Computational Insights into the Structural Dynamics of the Fc Fragment of IgG1 Subtype from Biosimilar VEGF-Trap

The constant fragment (Fc) of the Immunoglobulin G1 (IgG1) subtype is increasingly recognized as a crucial scaffold in the development of advanced therapeutics due to its enhanced specificity, efficacy, and extended half-life. A prime example is VEGF-Trap (Aflibercept), a recombinant fusion protein that merges the Fc region of the IgG1 subtype with the binding domains of vascular endothelial growth factor receptors (VEGFR)-1 and VEGFR-2. The Fc regions role in N-glycosylation is particularly important, as it significantly influences protein stability. In this study, we present the first near-physiological temperature structures of the N-glycan-bound Fc fragment of IgG1 subtype from a biosimilar VEGF-Trap, determined using the SPring-8 Angstrom Compact free electron LAser (SACLA) and the Turkish Light Source (Turkish DeLight). Comparative analysis with cryogenic structures, including our own data, reveals alternate conformations within the glycan-binding pocket. Furthermore, molecular dynamics (MD) simulations highlight an unexpected degree of structural plasticity. These findings offer new insights into the molecular basis of Fc-mediated functions and provide valuable information for the design of next-generation therapeutics.

molecular biology↗

bioRxiv2023

A DNA condensation code for linker histones

Linker histones play an essential role in chromatin packaging by facilitating compaction of the 11-nm fibre of nucleosomal "beads on a string". The result is a heterogeneous condensed state with local properties that range from dynamic, irregular and liquid-like, to stable and regular structures (the 30-nm fibre), which in turn impact chromatin-dependent activities at a fundamental level. The properties of the condensed state depend on the type of linker histone, particularly on the highly disordered C-terminal tail, which is the most variable region of the protein, both between species, and within the various subtypes and cell-type specific variants of a given organism. We have developed an in-vitro model system comprising linker histone tail and linker DNA, which although very minimal, displays surprisingly complex behaviour, and is sufficient to model the known states of linker-histone-condensed chromatin: disordered "fuzzy" complexes ("open" chromatin), dense liquid-like assemblies (dynamic condensates) and higher-order structures (organised 30-nm fibres). A crucial advantage of such a simple model is that it allows the study of the various condensed states by NMR, CD and scattering methods. Moreover, it allows capture of the thermodynamics underpinning the transitions between states through calorimetry. We have leveraged this to rationalise the distinct condensing properties of linker histone subtypes and variants across species that are encoded by the amino acid content of their C-terminal tails. Three properties emerge as key to defining the condensed state: charge density, lysine/arginine ratio, and proline-free regions, and we evaluate each separately using a strategic mutagenesis approach.

biophysics↗

bioRxiv2023

4D Crystallography Captures Transient IF1-Ribosome Dynamics in Translation Initiation

Initiation factor 1 (IF1) is one of multiple key ligands involved in the initiation of mRNA translation, a highly dynamic and carefully-orchestrated process. However, details surrounding IF1 transient interactions with the small 30S ribosomal subunit remain incompletely understood despite characterization of unbound and fully-bound 30S states. Improvements in X-ray light sources and crystallographic techniques are now enabling time-resolved structural studies at near-physiological temperature and near-atomic resolution and thus the structural investigation of such dynamic processes. Here, we employed time-resolved serial femtosecond X-ray crystallography (TR-SFX) to probe the binding of IF1 to the small 30S ribosomal subunit in real time. Our time-resolved structural data demonstrates transient cryptic short-, mid-, and long-range allostery among different regions of the small 30 ribosomal subunit during IF1 binding, revealing small- and large-scale protein-target interactions and dynamics within intermediate macromolecular states at unprecedented temporal and spatial resolution. These data represent one of the first such 4D crystallographic studies assessing protein-protein and protein-RNA interactions and could serve as the basis for subsequent studies of the ribosome and of the multitudinous dynamic processes which underpin biology, and therefore, of life.

biophysics↗

bioRxiv2023

Ambient Temperature Bacterial Large Ribosomal Subunit Structure Enabled by Serial Femtosecond X-ray Crystallography

Ribosomes are the supramolecular complexes responsible for protein synthesis. The large 50S ribosomal subunit catalyzes the peptidyl transferase reaction and peptide bond formation between amino acids. The 50S is targeted by many known clinically effective antibiotics. Available structures, obtained at cryogenic temperatures (CT), are used for drug discovery despite that active or important target sites may display a structural configuration that is CT-induced. The introduction of ultrafast and ultrabright X-ray free electron laser (XFEL) pulses has enabled the structural observation of biological macro- and supramolecules at previously unattainable, near-physiological temperatures. In this study, we use ultrafast and ultrabright XFEL pulses to solve the apo form of 50S ribosomal subunit isolated from the extremely thermophilic bacterium Thermus thermophilus at ambient temperature (AT). The dimeric structure of the 50S subunit presented in this work is among the largest ([~]3 megadalton) structures determined using an XFEL source to date. This study demonstrates the ability to obtain new information about ribosome structural dynamics at AT through serial femtosecond X-ray crystallography (SFX). This allowed us to capture previously unobserved dynamics of ribosomal protein uL23 and coordination by hexahydrated magnesium cations at a hitherto unseen resolution at near-physiological temperature. Also, residue A2602, at the core of the peptidyl transferase center (PTC), shows a rather different orientation of the sugar moiety if compared to CT structures. In addition, our structure highlights the importance of flexible residues at both the PTC and in the binding sites for antibiotics erythromycin and chloramphenicol. The method implemented here may also serve as a starting point for future structural research involving the 50S subunit complexes by employing time-resolved mix-inject and probe kineto-crystallography experiments at XFELs. Unveiling ligand-dependent 50S dynamics at physiological temperatures shall guide further development of next-generation antibiotics that target the translation machinery.

biophysics↗

bioRxiv2022

Comparative Study of High-resolution LysB29(Nε-myristoyl) des(B30) Insulin Structures Display Novel Dynamic Causal Interrelations in Monomeric-Dimeric Motions

The treatment of insulin-dependent diabetes mellitus is characterized by artificial supplementation of pancreatic {beta}-cell ability to regulate sugar levels in the blood. Even though various insulin analogs are crucial for reasonable glycemic control, understanding the dynamic mechanism of the insulin analogs may help to improve the best-protracted insulin analog to assist people with Type 1 Diabetes (T1D) to live comfortably while maintaining tight glycemic control. Here we present the high-resolution crystal structure of NN304, known as insulin detemir, to 1.7 [A] resolution at cryogenic temperature. We computationally further investigated our crystal structures monomeric-dimeric conformation and dynamic profile by comparing it with a previously available detemir structure (PDB ID: 1XDA). Our structure (PDB ID: 8HGZ) obtained at elevated pH provides electrostatically triggered minor movements in the equilibrium between alternate conformational substates compared to the previous structure, suggesting it might induce an intermediate state in the dissociation pathway of the insulin detemirs hexamer:dihexamer equilibrium. Supplemented with orientational cross-correlation analysis by Gaussian Network Model (GNM), this alternate oligomeric conformation offers the distinct cooperative motions originated by loose coupling of distant conformational substates of a protracted insulin analog that has not been previously observed.

biophysics↗

bioRxiv2022

Rapid and High Resolution Ambient Temperature Structure Determination at Turkish Light Source

High-resolution biomacromolecular structure determination is essential to better understand protein function and dynamics. Serial crystallography is an emerging structural biology technique which has fundamental limitations due to either sample volume requirements or immediate access to the competitive X-ray beamtime. Obtaining a high volume of well-diffracting, sufficient-size crystals while mitigating radiation damage remains a critical bottleneck of serial crystallography. As an alternative, we introduce the plate-reader module adapted for using a 72-well Terasaki plate for biomacromolecule structure determination at a convenience of a home X-ray source. We also present the first ambient temperature lysozyme structure determined at the Turkish Light Source (Turkish DeLight). The complete dataset was collected in 18.5 mins with resolution extending to 2.39 [A] and 100% completeness. Combined with our previous cryogenic structure (PDB ID: 7Y6A), the ambient temperature structure provides invaluable information about the structural dynamics of the lysozyme. Turkish DeLight provides robust and rapid ambient temperature biomacromolecular structure determination with limited radiation damage.

biophysics↗

bioRxiv2022

Cryogenic X-ray crystallographic studies of biomacromolecules at Turkish Light Source: Turkish DeLight

X-ray crystallography is a robust and powerful structural biology technique that provides high-resolution atomic structures of biomacromolecules. Scientists use this technique to unravel mechanistic and structural details of biological macromolecules (e.g. proteins, nucleic acids, protein complexes, protein-nucleic acid complexes, or large biological compartments). Since its inception, single-crystal cryo-crystallography has never been performed in Turkiye due to the lack of a single-crystal X-ray diffractometer. The X-ray diffraction facility recently established at the University of Health Sciences, Istanbul, Turkiye will enable Turkish and international researchers to easily perform high-resolution structural analysis of biomacromolecules from single crystals. Here, we describe the technical and practical outlook of a state-of-the-art home-source X-ray, using lysozyme as a model protein. The methods and practice described in this article can be applied to any biological sample for structural studies. Therefore, this article will be a valuable practical guide from sample preparation to data analysis.

biophysics↗

bioRxiv2021

Cooperative Allostery and Structural Dynamics of Streptavidin at Cryogenic- and Ambient-temperature

Multimeric protein assemblies are abundant in nature. Streptavidin is an attractive protein that provides a paradigm system to investigate the intra- and intermolecular interactions of multimeric protein complexes. Also, it offers a versatile tool for biotechnological applications. Here, we present two apo-streptavidin structures, the first one is an ambient temperature Serial Femtosecond X-ray crystal (Apo-SFX) structure at 1.7 [A] resolution and the second one is a cryogenic crystal structure (Apo-Cryo) at 1.1 [A] resolution. These structures are mostly in agreement with previous structural data. Combined with computational analysis, these structures provide invaluable information about structural dynamics of apo streptavidin. Collectively, these data further reveal a novel cooperative allostery of streptavidin which binds to substrate via water molecules that provide a polar interaction network and mimics the substrate biotin which displays one of the strongest affinities found in nature.

biophysics↗

bioRxiv2021

Structural Insights into Bifunctional Thaumarchaeal Crotonyl-CoA Hydratase and 3-Hydroxypropionyl-CoA Dehydratase from Nitrosopumilus maritimus

The ammonia-oxidizing thaumarchaeal 3-hydroxypropionate/4-hydroxybutyrate (3HP/4HB) cycle is one of the most energy-efficient CO2 fixation cycles discovered thus far. The protein encoded by Nmar_1308 (from Nitrosopumilus maritimus SCM1) is a promiscuous enzyme that catalyzes two essential reactions within the thaumarchaeal 3HP/4HB cycle, functioning as both a crotonyl-CoA hydratase (CCAH) and 3- hydroxypropionyl-CoA dehydratase (3HPD). In performing both hydratase and dehydratase activities, Nmar_1308 reduces the total number of enzymes necessary for CO2 fixation in Thaumarchaeota, reducing the overall cost for biosynthesis. Here, we present the first high-resolution crystal structure of this bifunctional enzyme with key catalytic residues in the thaumarchaeal 3HP/4HB pathway.

biochemistry↗

bioRxiv2021

Structural insight into host plasma membrane association and assembly of HIV-1 Matrix protein

HIV-1 continues to be a global health concern since AIDS was first recognized by the World Health Organization (WHO). It is estimated that there were 38 million people infected with HIV-1 and 1.5 million deaths in 2019 alone. A better understanding of the details of the HIV late-stage life cycle, involving Pr55Gag attachment to the membrane for the further oligomerization to release virion, will provide us new avenues for potential treatment. Inositol hexakisphosphate (IP6) is an abundant endogenous cyclitol molecule and its binding was linked to the oligomerization of Pr55Gag via the MA domain. However, the binding site of IP6 on MA was unknown and the structural details of this interaction were missing. Here, we present three high-resolution crystal structures of the MA domain in complex with IP6 molecules to reveal its binding mode. Additionally, extensive Differential Scanning Fluorimetry analysis combined with cryo- and ambient-temperature X-ray crystallography and computational biology identify the key residues that participate in IP6 binding. Our data provide novel insights about the multilayered HIV-1 virion assembly process that involves the interplay of IP6 with PIP2, a phosphoinositide essential for the membrane binding of Pr55Gag. IP6 and PIP2 have neighboring alternate binding sites within the same highly basic region (residues 18-33). This indicates that IP6 and PIP2 bindings are not mutually exclusive and may play a key role in coordinating virion particles membrane localization. Based on our three different IP6-MA complex crystal structures, we propose a new model that involves the IP6 coordination of the oligomerization of outer MA and inner CA domain 2D layers during assembly and budding.

microbiology↗

bioRxiv2020

Near-Physiological-Temperature Serial Femtosecond X-ray Crystallography Reveals Novel Conformations of SARS-CoV-2 Main Protease Active Site for Improved Drug Repurposing

The COVID19 pandemic has resulted in 25+ million reported infections and nearly 850.000 deaths. Research to identify effective therapies for COVID19 includes: i) designing a vaccine as future protection; ii) structure-based drug design; and iii) identifying existing drugs to repurpose them as effective and immediate treatments. To assist in drug repurposing and design, we determined two apo structures of Severe Acute Respiratory Syndrome CoronaVirus-2 main protease at ambienttemperature by Serial Femtosecond X-ray crystallography. We employed detailed molecular simulations of selected known main protease inhibitors with the structures and compared binding modes and energies. The combined structural biology and molecular modeling studies not only reveal the dynamics of small molecules targeting main protease but will also provide invaluable opportunities for drug repurposing and structure-based drug design studies against SARS-CoV-2. One Sentence SummaryRadiation-damage-free high-resolution SARS-CoV-2 main protease SFX structures obtained at near-physiological-temperature offer invaluable information for immediate drug-repurposing studies for the treatment of COVID19.

biophysics↗