Biochemistry, Biophysics, and Structural Biology Commons^™

Through The Back Door: Proteins Escape Cells Without Conventional Permission, Michael J. Cohen

Dissertations, Theses, and Capstone Projects

Proteins secreted to the extracellular environment play a fundamental role as signals, in metabolism, and a variety of other processes. The process of secretion through the endoplasmic reticulum and Golgi to the plasma membrane is well documented, and all cargo in this pathway contains a signal peptide. However, a variety of proteins secreted from eukaryotes lack a signal peptide and are called unconventionally secreted proteins. Here we discuss known mechanisms of unconventional protein secretion, as well as model proteins which follow characterized pathways. Additionally, we summarize the roles various unconventionally secreted proteins play outside of cells and suggest criteria for …

Hur Ubiquitination By Brca1/Bard1 And Its Role In Controlling Gene Expression During Dna Damage Response, Gamage M. Aruggoda

Dissertations, Theses, and Capstone Projects

Despite our understanding of the biochemistry of the BRCA1/BARD1 E3 ligase, we know very little of the mechanism by which its cellular substrates, how they are chosen, how its E3 Ub ligase activity is regulated, which are the cofactors involved in this regulation, and how the substrates are modified during DDR. In this dissertation, I further evaluate BRCA1/BARD1-mediated E3 ligase activity and how CstF-50 and p97 regulate this reaction working as cofactors. My data show that BRCA1/BARD1 is an E3 ligase that ubiquitinates the RNA binding protein Human antigen R(HuR).

HuR is abundant in the nucleus and is transported to …

Advanced Computational Methodologies To Study Binding Free Energies Of Biomolecular Complexes, Rajat Kumar Pal

Dissertations, Theses, and Capstone Projects

Molecular recognition is the basis of biological mechanisms and is a key element to consider while formulating effective and safe drugs. Pharmaceutical drugs are designed so as to bind a target protein even at very low concentrations to alter the diseased conditions without interfering with normal biological processes. In a rational drug design process, this is achieved by acquiring information about the chemical structure and the physical and chemical properties of the target protein receptor to gain insights on how changing the chemical composition of the substrate drug could affect the protein-drug interaction and binding affinities. Computational models are used …

Mutational Analysis And Domain Characterization Of The Apolipoprotein L-1 Ion Channel, Charles M. Schaub

Dissertations, Theses, and Capstone Projects

The human innate immunity factor Apolipoprotein L-1 (APOL1) protects against Trypanosoma brucei brucei infection. Recent studies have shown recombinant APOL1 (rAPOL1) inserts into planar lipid bilayers at an acidic pH 5.6 and forms a cation-selective channel, which opens upon subsequent neutralization, pH 7.2. This corresponds with the pH changes APOL1 would encounter during endosome recycling, suggesting that APOL1 forms a pH-gated ion channel in the plasma membrane of the parasite, leading to uncontrolled ion flux and osmotic imbalance. However, structural and domain characteristics of the APOL1 channel are poorly understood, despite potential similarities to diphtheria and colicin toxins. Utilizing E. …

Exploration Of The Inhibitory Properties Of The Nucleoside Antibiotic Salicyl-Ams And Analogues Targeting Siderophore Biosynthesis In Mycobacterium Tuberculosis, Glennon Bythrow

Dissertations, Theses, and Capstone Projects

Mycobacterium tuberculosis (Mtb) is a resilient, obligate bacterial pathogen responsible for pulmonary tuberculosis disease (TB), that has upheld a significant impact on global public health throughout history. The World Health Organization (WHO) approximates nearly 10 million new TB cases arose in 2017 alone, accounting for 1.6 million deaths. There has been a notable rise in TB cases produced by multidrug‑resistant (MDR) and extensively drug-resistant (XDR) strains of Mtb. This, along with the intrinsic resistance of Mtb to many standard drugs and poor patient compliance, is deeply impacting global control of TB. Among the several strategies currently in …

Hyaluronan At The Brain-Environment Interface, Donald M. Thevalingam

Dissertations, Theses, and Capstone Projects

Hyaluronan (HA; Hyaluronic Acid), a primary scaffolding component of the brain extracellular matrix, serves as an integral structural component to the brain extracellular space (ECS). The fossorial African naked mole-rat (Heterocephalus glaber; NM-R), a mammal which lives in a low-oxygen environment and is capable of tolerating hypoxia and hypercapnia, has been shown to synthesize and sustain a unique high-molecular-mass variant of hyaluronan macromolecule (HMM-HA). This body of work highlights HA’s role in mediating the interplay between brain ECM composition, ECS structure, and cell viability.

Here we employ the NM-R as a unique animal model to observe the role of the …

Towards A Mathematical Model Of Motility Using Dictyostelium Discoideum: Proteins And Geometric Features That Regulate Bleb-Based Motility, Zully Santiago

Dissertations, Theses, and Capstone Projects

A variety of biological functions depend on actin organization. The organization of actin is tightly regulated by a plethora of extracellular and intracellular signaling, scaffolding, and actin-binding proteins. Dysfunctions in this regulation lead to immune diseases, increased susceptibility to pathogens, neurodegenerative diseases, developmental disorders, and cancer metastasis. A variety of actin-dependent processes, including cell motility, are regulated by several proteins of interest: Paxillin, a scaffolding protein; WASP, an actin nucleating protein; SCAR/WAVE, another WASP family actin nucleating protein; Talin, a cortex-to-membrane binding protein; Myosin II, an F-actin contracting motor protein; and Protein Kinase C, a protein kinase. D. discoideum cells …

Characterization Of Early Biofilm Formation And Physiology In Neisseria Gonorrhoeae, Kelly Eckenrode

Dissertations, Theses, and Capstone Projects

Many bacteria rely on the dynamics of their extracellular appendages to perform important tasks, like motility and biofilm formation. Interestingly, these dynamics have been linked to physiological responses in some pathogenic bacteria; therefore, it is important to understand more about the role of physical forces in bacteria. I used the causative agent of the human disease gonorrhea, Neisseria gonorrhoeae, as a model system to study the role of physical force on early biofilm formation. The advantage of this system is that cell-cell interactions are controlled by extracellular filaments called type IV pili (tfp). Tfp is composed of monomers that give …

Developing A Dissociative Nanocontainer For Peptide Drug Delivery, Michael Patrick Kelly

Dissertations, Theses, and Capstone Projects

The potency and specificity of bioactive peptides have propelled these agents to the forefront of pharmacological research. However, delivery of peptides to their molecular target in cells is a major obstacle to their widespread application. A Trojan Horse strategy of packaging a bioactive peptide within a modified protein cage to protect it during transport, and releasing it at the target site, is a promising delivery method. Recent work has demonstrated that the viral capsid of the P22 bacteriophage can be loaded with an arbitrary, genetically-encoded peptide, and externally decorated with a cell-penetrating peptide, such as HIV-Tat, to translocate across in …

Innate Antibodies, Murine Models, And Evolution: A Study Of Trypanosome Lytic Factor Functions And Their Translational Applications, Joseph P. Verdi

Dissertations, Theses, and Capstone Projects

Trypanosome lytic factors (TLFs) are primate-specific antimicrobial protein complexes that lyse African trypanosome parasites by delivering the channel-forming toxin APOL1 to the invading microorganisms. Human serum contains two TLFs that are delivered to the parasite by separate mechanisms, only one of which has been characterized. TLF1 is endocytosed by a receptor that is typically blocked by other serum factors in vivo, suggesting that TLF2 is the more relevant lytic factor in the context of trypanosome immunity. TLF2 is non-covalently associated with polyclonal immunoglobulin M (IgM) antibodies, which we report here to be involved in the uptake mechanism. The TLF2-IgMs …

Renal Specific Rnai Delivery By Fibrillar Nanoparticle Excipients, Sam Wong

Dissertations, Theses, and Capstone Projects

RNA interference (RNAi) is a powerful tool to manipulate the phenotype of an organism by silencing the expression of specific genes and is viewed as a highly promising platform for treating undruggable targets and disorders where small molecule drugs and antibodies would fail. However, development of RNAi based therapies has faced major barriers including cellular and tissue-specific uptake of the Small Interfering RNA (siRNA). Utilizing different nanoparticles as RNAi excipients, cellular uptake and gene silencing potency can be greatly improved. The research in Dr. McDevitt groups has fibrillar carbon nanotubes (CNT) as carriers for siRNA for gene silencing in vitro …

Systematics Of Carex Section Laxiflorae (Cyperaceae), Jenna Dorey

Dissertations, Theses, and Capstone Projects

Carex, with more than 2100 species, is the most species-rich genus of flowering plants in temperate regions of the world. Members of the family Cyperaceae are colloquially known as sedges, and members of the genus Carex are called “true sedges.” Carex occur on every continent except for Antarctica, they thrive in a panoply of habitats, and are ecologically important as a forage source for wildlife, carbon sequestration, prevention of soil erosion, and providing habitat for fresh water invertebrates. Despite their importance many sedges are still poorly known, such as the woodland sedges in Carex section Laxiflorae, which is …

Minimalistic Peptide-Based Supramolecular Systems Relevant To The Chemical Origin Of Life, Daniela Kroiss

Dissertations, Theses, and Capstone Projects

All forms of life are based on biopolymers, which are made up of a selection of simple building blocks, such as amino acids, nucleotides, fatty acids and sugars. Their individual properties govern their interactions, giving rise to complex supramolecular structures with highly specialized functionality, including ligand recognition, catalysis and compartmentalization. In this thesis, we aim to answer the question whether short peptides could have acted as precursors of modern proteins during prebiotic evolution. Using a combination of experimental and computational techniques, we screened a large molecular search space for peptide sequences that are capable of forming supramolecular complexes with adenosine …

Molecular Dynamics Simulations Of Supramolecular Assemblies In Biology And Bionanotechnology, Anjela Manandhar

Dissertations, Theses, and Capstone Projects

Molecular self-assembly is an energy driven process where randomly organized building blocks interact noncovalently to form highly organized supramolecular nanostructures. In biology, the cytoskeleton is a classic example of a dynamic self-assembly, forming long filamentous structures from monomeric protein subunits. Similarly, the self-assembly process is widely exploited in nanotechnology to build bio-functional nanostructures. In this work, we studied biological (microtubule) and synthetic (peptide drug amphiphile nanotube) self-assembled systems. We utilized long time-scale molecular dynamics simulation to investigate the structural and dynamical properties of these systems.

At the molecular level, the dynamic instability (random growth and shrinkage) of the microtubule (MT) …

Characterization Of Extracellular Vesicles From Human Diabetic Retinopathy Retinal Tissue In Vitro And From Urine Of Human Patients With Diabetic Retinopathy, Jason Mighty

Dissertations, Theses, and Capstone Projects

Diabetic Retinopathy (DR) is a neurovascular complication associated with diabetes mellitus that affects approximately 120 million people worldwide and its prevalence is expected to reach 190 million by 2030. DR diagnosis is accomplished with fundus ophthalmoscopy often when retinal damage and vision loss have already occurred. A group of biomarker being explored for early detection of diseases are extracellular vesicles (EVs), which are nanometer diameter lipid enclosed vesicles, released from all cell types and containing genetic cargo reflective of releasing cell state. EV biomarkers are currently being explored to help monitor disease predisposition, pathogenesis and response to treatment. While an …

The Role And Regulation Of Alternative Polyadenylation In The Dna Damage Response, Michael R. Murphy

Dissertations, Theses, and Capstone Projects

Cellular homeostasis is achieved by the dynamic flux in gene expression. Post-transcriptional regulation of coding and non-coding RNA offers a fast method of adapting to a changing cellular environment, including deadenylation, microRNA (miRNA) pathway, and alternative polyadenylation (APA). In this dissertation, I explored some of the mechanisms involved in the post-transcriptional regulation of gene expression. The main hypothesis in these studies is that a single APA event after DNA damage is governed by specific conditions and factors outside of current known regulators of APA, and that the resultant transcript has a role in the DNA damage response (DDR). My aims …

Characterization Of Immunomodulatory Microbial Factors In Medicinal Plants, Kriti Kalpana

Dissertations, Theses, and Capstone Projects

Medicinal plants are one of the biggest sources of natural products with therapeutic importance. There are currently over 28,000 plants with putative medicinal values. Plant-derived compounds have been explored extensively for various biological activities ranging from anti-cancer, immune-boosting to anti-inflammatory and anti-oxidant. Some of the most important therapeutic agents are of plant-origin, such as paclitaxel from Pacific yew (Taxus brevifolia) and artemisinin from qinghao su (a Chinese medicinal herb; a.k.a. Artemisia annua) to name a few.

The study presented in this thesis started out as classical pharmacognosy research, which focused on the identification of immunostimulatory factors in …

Solvation Thermodynamic Mapping In Computer Aided Drug Design, Steven Ramsey

Dissertations, Theses, and Capstone Projects

The displacement of water from surfaces upon biomolecular recognition and association makes a significant contribution to the free energy changes of these processes. We therefore posit that accurate characterization of local structural and thermodynamic molecular water properties can improve computational model accuracy and predictivity of recognition and association processes. In this thesis, we discuss Solvation Thermodynamic Mapping (STM) methods that we have developed using inhomogeneous fluid solvation theory (IST) to better characterize active site water structural and thermodynamic properties on protein surfaces and the open source tools that we have developed, GIST-CPPTRAJ and SSTMap, which implement these methods which we …

The Determining Factors Of The Self-Assembly Of Collagen Mimetic Peptide, Fangfang Chen

Dissertations, Theses, and Capstone Projects

We recently reported that a designed triple helix Col108 self-associates to form collagen-like mini-fibrils having a d-periodicity of 35 nm. Recombinant protein Col108 consists of 378-residue triple helix domain organized into three repeating sequence units, and a C-terminal foldon domain. The 35 nm d-period of Col108 mini-fibrils is consistent with the one unit staggered arrangement of the associating helices. To further investigate if the sequence periodicity is crucial for collagen mimetic peptide fibril formation, we studied the self-assembly of four other designed triple helical peptides. Peptide 2U108 has two repeating sequence units; peptide Col877 consists of three repeating …

Pretargeted Radioimmunotherapy Utilizing The Inverse Electron Demand Diels-Alder Reaction, Rosemery Membreno

Dissertations, Theses, and Capstone Projects

Radioimmunotherapy capitalizes on the specificity and affinity of antibodies for their antigens to localize radioactivity at the tumor site. One limitation in using antibodies is their long circulation time, which can take days to weeks to fully clear from blood circulation. When a radioisotope is directly conjugated to this immunoglobulin vector, the red marrow and other healthy organs are receiving a constant radiation dose while it is in blood circulation. This not only harms healthy organs, but limits the dose of radioactivity that can be administered thus prolonging treatment. A promising alternative to limit the radiation dose to non-tumor tissue …

Bisthioether Stapled Peptides Targeting Polycomb Repressive Complex 2 Gene Repression, Gan Zhang

Dissertations, Theses, and Capstone Projects

Interactions between proteins play a key role in nearly all cellular process, and therefore, disruption of such interactions may lead to many different types of cellular dysfunctions. Hence, pathologic protein-protein interactions (PPIs) constitute highly attractive drug targets and hold great potential for developing novel therapeutic agents for the treatment of incurable human diseases. Unfortunately, the identification of PPI inhibitors is an extremely challenging task, since traditionally used small molecule ligands are mostly unable to cover and anchor on the extensive flat surfaces that define those binary protein complexes. In contrast, large biomolecules such as proteins or peptides are ideal fits …

Ck2 Negatively Regulates 5-Ht4 Receptor Signaling In The Prefrontal Cortex And Mediates Depression-Like Behaviors, Julia Castello Saval

Dissertations, Theses, and Capstone Projects

The serotonergic system has been the major candidate in the pathophysiology of mood related disorders such as anxiety and major depressive disorder (MDD). Unfortunately, current antidepressant drugs are ineffective in 50% of the population and require chronic administration for a period of 3-6 weeks before the onset of therapeutic response. 5-HT4 receptor (5-HT₄R) agonists have emerged as potential candidates for fast antidepressant action, since an antidepressant response can be achieved after 3 days of pharmacological administration in rodents.

This dissertation aims to investigate the role of casein kinase 2 (CK2) as a regulator of 5-HT₄R expression …

Structural Studies On Calcium/Calmodulin-Dependent Activation Of Eukaryotic Elongation Factor 2 Kinase, Kwangwoon Lee

Dissertations, Theses, and Capstone Projects

Eukaryotic elongation factor 2 kinase (eEF-2K) is a key modulator of the rate of protein synthesis. Activated by calcium-loaded calmodulin (Ca²⁺-CaM), eEF-2K phosphorylates its only known physiological substrate, eEF-2, on a specific threonine residue (Thr-56). Phosphorylated eEF-2 has reduced affinity for the ribosome, and results in a significant decrease in the rate of translation elongation. Modulation of the rate of translation elongation plays a crucial role in proteostasis – adequate regulation of protein synthesis, protein folding, and protein degradation that greatly influences cellular growth and survival. Binding of Ca²⁺-CaM triggers activation of eEF-2K and remains intact …

Supercharged Models Of Intrinsically Disordered Proteins And Their Utility In Sensing, Peter J. Schnatz

Dissertations, Theses, and Capstone Projects

In this thesis I show that greatly increasing the magnitude of a protein’s net charge using surface supercharging transforms that protein into a ligand-gated or counterion-gated conformational molecular switch. To demonstrate this I first modified the designed helical bundle hemoprotein H4 using simple molecular modeling, creating a highly charged protein which both unfolds reversibly at low ionic strength and undergoes the ligand-induced folding transition commonly observed in signal transduction by intrinsically disordered proteins in biology. Due to the high surface charge density, ligand binding to this protein is allosterically activated by low concentrations of divalent cations and the polyamine spermine. …

Towards An Atomic Level Model Of The Structure And Calmodulin Mediated Activation Of Eef-2k, Nathan E. Will

Dissertations, Theses, and Capstone Projects

Eukaryotic elongation factor 2 kinase (eEF-2K), the only calmodulin (CaM) dependent member of the a-kinase, phosphorylates eukaryotic elongation factor 2 (eEF-2) on a specific residue (Thr-56), decreasing its affinity for the ribosome and reducing the rate of peptide chain elongation during protein translation. In contrast to the “release-of-inhibition’ mechanism operative in most CaM-dependent proteins kinases, the activation of eEF-2K is proposed to occur through a two-step process subsequent to the engagement of CaM and involves (1) auto-phosphorylation on T348 and (2) engagement of an allosteric site by phospho-T348 leading to a state with the highest activity towards the substrate eEF-2. …

Phospholipase D-Dependent Mtorc1 Activation By Glutamine, Elyssa Bernfeld

Dissertations, Theses, and Capstone Projects

Glutamine, the conditionally essential amino acid and most abundant amino acid in human sera, is a key nutrient required for sustaining cell proliferation. Glutamine is essential for nucleotide, protein, and lipid synthesis, all of which are essential for cell proliferation. The mammalian target of rapamycin complex 1 (mTORC1) is a highly conserved protein complex that acts as a sensor of nutrients, relaying signals for the shift from catabolic to anabolic metabolism. While glutamine plays an important role in activating mTORC1, the mechanism is not completely clear. Here we describe a Rag-independent mechanism of mTORC1 activation by glutamine that is dependent …

Mechanisms Adopted By Dengue-2 Viruses To Induce Autophagy In Mammalian Cells, Sounak Ghosh Roy

Dissertations, Theses, and Capstone Projects

Dengue, the most rapidly spreading flavivirus, threatens to affect almost half of the human global population. We previously showed that dengue-2 protects canine kidney cells (MDCK) from cytotoxic chemicals. We showed, independently, that cell protection, as well as viral replication and maturation, are positively regulated by PI3K-dependent autophagy. However, we had not identified the specific pathway that induces autophagy in infected cells. The current study explores the role of a specific branch of the endoplasmic reticulum (ER) stress-mediated Unfolded Protein Response (UPR), the PERK/eIF2α/ATF4 pathway in the induction of autophagy by …

Renal Risk Variants Of Apolipoprotein L-1 Form Channels At The Plasma Membrane That Lead To A Cytotoxic Influx Of Calcium, Joseph A. Giovinazzo

Dissertations, Theses, and Capstone Projects

Apolipoprotein L-1 (APOL1) is a secreted protein that provides protection against several protozoan parasites due to its channel forming properties. Recently evolved variants, G1 and G2, increase kidney disease risk when present in two copies. In mammalian cells, overexpression of G1 and G2, but not wild-type G0, leads to swelling and eventual lysis. However, the mechanism of cell death remains elusive with multiple pathways being invoked, such as autophagic cell death mediated by a BH3 domain in APOL1, which we evaluated in this study. We hypothesized that the common trigger for these pathways is the APOL1 cation channel, which is …

Binding Of Maize Necrotic Streak Virus (Mnesv) 3’ I-Shaped Structure (3’ Iss) To Eukaryotic Translation Factors (Eifs) And Implication In Eif4f Mediated Translation Initiation, Qiao Liu

Dissertations, Theses, and Capstone Projects

5' m⁷GpppN cap and the 3' poly adenosine (A) tail of eukaryotic mRNAs are key elements for recruiting translation initiation machinery in canonical translation initiation. Unlike host mRNAs, many viruses lack these elements and yet they are translated efficiently. Plant viruses, in particular, have complex structures within their untranslated regions (UTR) that allow them to bypass some cellular translation control steps. In Maize necrotic streak virus (MNeSV) 3' UTR, an I-Shaped RNA Structure (ISS) has been reported to mediate the virus translation initiation progress. 3’ ISS binding with eIF4F has been shown to facilitate translation. 5’ -3’ kissing …

Mechanism And Development Of Peptide-Based Inhibitors To Human Islet Amyloid Polypeptide (Hiapp) Self-Assembly, Jayson Vedad

Dissertations, Theses, and Capstone Projects

Amyloid fibrils formed by of hIAPP_1-37 (also known as amylin) has been linked to type-II diabetes mortalities and its formation was found to be related to the three aromatic residues in hIAPP_1-37. In this dissertation, the role of aromatic amino acids, particularly that of Phe-23, and its various interactions to the self-assembly of human islet amyloid polypeptide (hIAPP)_22-29 were investigated. Using a variety of spectroscopic techniques with emphasis to vibrational spectroscopy (FT-IR and Raman spectroscopies) in conjunction with computational methods, different factors leading to aggregation as well as its inhibition were identified. Among the driving forces …