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Altering Oligomerization Of Epha2 Via Mutations In The Intracellular Domain, Ryan W. Lingerak 2018 The University of Akron

Altering Oligomerization Of Epha2 Via Mutations In The Intracellular Domain, Ryan W. Lingerak

Honors Research Projects

Eph receptor tyrosine kinases (RTKs) are activated by membrane-bound ligands called ephrins. Eph RTKs are divided into two subclasses, each activated by a specific classes of the ligand ephrin. The overexpression of Eph receptors is correlated to cancer cell metastasis in several different types of cancers. Studies with the EphA2 extracellular domain (ECD) and ephrinA1 ligand have shown that upon binding of ephrin to the receptor, EphA2 undergoes increased oligomerization and activation. This indicates that oligomerization is intimately connected to kinase activity. High resolution crystal structures of the EphA2 ECD have revealed some details of these ligand bound oligomers, as ...


Tea Induction Of Cyp6a8 Promoter In Drosophila Melanogaster, Fiona Retzer 2017 University of Tennessee, Knoxville

Tea Induction Of Cyp6a8 Promoter In Drosophila Melanogaster, Fiona Retzer

University of Tennessee Honors Thesis Projects

No abstract provided.


Crystal Structure Of Apobec3a Bound To Single-Stranded Dna Reveals Structural Basis For Cytidine Deamination And Specificity, Takahide Kouno, Tania V. Silvas, Brendan J. Hilbert, Shivender Shandilya, Markus-Frederik Bohn, Brian A. Kelch, William E. Royer, Mohan Somasundaran, Nese Kurt Yilmaz, Hiroshi Matsuo, Celia A. Schiffer 2017 University of Massachusetts Medical School

Crystal Structure Of Apobec3a Bound To Single-Stranded Dna Reveals Structural Basis For Cytidine Deamination And Specificity, Takahide Kouno, Tania V. Silvas, Brendan J. Hilbert, Shivender Shandilya, Markus-Frederik Bohn, Brian A. Kelch, William E. Royer, Mohan Somasundaran, Nese Kurt Yilmaz, Hiroshi Matsuo, Celia A. Schiffer

Celia A. Schiffer

Nucleic acid editing enzymes are essential components of the immune system that lethally mutate viral pathogens and somatically mutate immunoglobulins, and contribute to the diversification and lethality of cancers. Among these enzymes are the seven human APOBEC3 deoxycytidine deaminases, each with unique target sequence specificity and subcellular localization. While the enzymology and biological consequences have been extensively studied, the mechanism by which APOBEC3s recognize and edit DNA remains elusive. Here we present the crystal structure of a complex of a cytidine deaminase with ssDNA bound in the active site at 2.2 A. This structure not only visualizes the active ...


Molecular Mechanisms Of C-Terminal Eps15 Homology Domain Containing (Ehd) Protein Function, Kriti Bahl 2017 University of Nebraska Medical Center

Molecular Mechanisms Of C-Terminal Eps15 Homology Domain Containing (Ehd) Protein Function, Kriti Bahl

Theses & Dissertations

Endocytic trafficking is not only an essential process for the maintenance of cellular homeostasis but also plays a vital role in regulating diverse cellular processes such as signaling, migration and cell division. The C-terminal Eps 15 Homology Domain proteins (EHD1-4) play pivotal roles in regulating distinct steps of endocytic trafficking. Among the EHDs, EHD2 is disparate both in terms of sequence homology (70%) and its subcellular localization at the caveolae. The crystal structure of EHD2 has been solved and it contains an unstructured loop consisting of two proline-phenylalanine (PF) motifs: KPFRKLNPF. However, the other paralogs EHD1, EHD3 ...


Blocking Deprotonation With Retention Of Aromaticity In A Plant Ent-Copalyl Diphosphate Synthase Leads To Product Rearrangement, Kevin C. Potter, Jiachen Zi, Young J. Hong, Samuel Schulte, Brandi Malchow, Dean J. Tantillo, Reuben J. Peters 2017 Iowa State University

Blocking Deprotonation With Retention Of Aromaticity In A Plant Ent-Copalyl Diphosphate Synthase Leads To Product Rearrangement, Kevin C. Potter, Jiachen Zi, Young J. Hong, Samuel Schulte, Brandi Malchow, Dean J. Tantillo, Reuben J. Peters

Reuben J. Peters

Biosynthesis of the labdane-related diterpenoids, a large superfamily of over 7,000 natural products, is characterized by the use of class II diterpene cyclases.[1] The vast majority of these biocatalysts are exclusively found in plants, stemming from repeated evolutionary diversification of the ent-copalyl diphosphate synthase (CPS) required for gibberellin phytohormone biosynthesis – i.e., via gene duplication and neofunctionalization.[2] As implied by this evolutionary scenario, these enzymes must exhibit catalytic plasticity that enables new products to readily arise. Consistent with this hypothesis, we have shown that substitution of smaller residues for the catalytic base group can lead to the ...


Efficient Heterocyclisation By (Di)Terpene Synthases, S. Mafu, K. C. Potter, M. L. Hillwig, S. Schulte, J. Criswell, R. J. Peters 2017 Iowa State University

Efficient Heterocyclisation By (Di)Terpene Synthases, S. Mafu, K. C. Potter, M. L. Hillwig, S. Schulte, J. Criswell, R. J. Peters

Reuben J. Peters

While cyclic ether forming terpene synthases are known, the basis for such heterocyclisation is unclear. Here it is reported that numerous (di)terpene synthases, particularly including the ancestral ent-kaurene synthase, efficiently produce isomers of manoyl oxide from the stereochemically appropriate substrate. Accordingly, such heterocyclisation is easily accomplished by terpene synthases. Indeed, the use of single residue changes to induce production of the appropriate substrate in the upstream active site leads to efficient bifunctional enzymes producing isomers of manoyl oxide, representing novel enzymatic activity.


A Functional Genomics Approach To Tanshinone Biosynthesis Provides Stereochemical Insights, Wei Gao, Matthew L. Hillwig, Luqi Huang, Guanghong Cui, Xueyong Wang, Jianqiang Kong, Bin Yang, Reuben J. Peters 2017 Chinese Academy of Chinese Medical Science

A Functional Genomics Approach To Tanshinone Biosynthesis Provides Stereochemical Insights, Wei Gao, Matthew L. Hillwig, Luqi Huang, Guanghong Cui, Xueyong Wang, Jianqiang Kong, Bin Yang, Reuben J. Peters

Reuben J. Peters

Tanshinones are abietane-type norditerpenoid quinone natural products that are the bioactive components of the Chinese medicinal herb Salvia miltiorrhiza Bunge. The initial results from a functional genomics-based investigation of tanshinone biosynthesis, specifically the functional identification of the relevant diterpene synthases from S. miltiorrhiza, are reported. The cyclohexa-1,4-diene arrangement of the distal ring poises the resulting miltiradiene for the ensuing aromatization and hydroxylation to ferruginol suggested for tanshinone biosynthesis.


A Single Residue Switch Converts Abietadiene Synthase Into A Pimaradiene Specific Cyclase, P. Ross Wilderman, Reuben J. Peters 2017 Iowa State University

A Single Residue Switch Converts Abietadiene Synthase Into A Pimaradiene Specific Cyclase, P. Ross Wilderman, Reuben J. Peters

Reuben J. Peters

Terpene synthases often catalyze complex cyclization reactions that typically represent the committed step in particular biosynthetic pathways, leading to great interest in their enzymatic mechanisms. We have recently demonstrated that substitution of a specific Ile with Thr was sufficient to “short circuit” the complex cyclization reaction normally catalyzed by ent-kaurene synthases to instead produce ent-pimaradiene. Here we report that the complex cyclization/rearrangement reaction catalyzed by abietadiene synthase can be similarly cut short to produce pimaradienes by an analogous Ser for Ala change, albeit with a slight shift in active site location to accommodate the difference in substrate ...


Strand-Specific Libraries For High Throughput Rna Sequencing (Rna-Seq) Prepared Without Poly(A) Selection, Zhao Zhang, William E. Theurkauf, Zhiping Weng, Phillip D. Zamore 2017 University of Massachusetts Medical School

Strand-Specific Libraries For High Throughput Rna Sequencing (Rna-Seq) Prepared Without Poly(A) Selection, Zhao Zhang, William E. Theurkauf, Zhiping Weng, Phillip D. Zamore

Zhao Zhang

BACKGROUND: High throughput DNA sequencing technology has enabled quantification of all the RNAs in a cell or tissue, a method widely known as RNA sequencing (RNA-Seq). However, non-coding RNAs such as rRNA are highly abundant and can consume >70% of sequencing reads. A common approach is to extract only polyadenylated mRNA; however, such approaches are blind to RNAs with short or no poly(A) tails, leading to an incomplete view of the transcriptome. Another challenge of preparing RNA-Seq libraries is to preserve the strand information of the RNAs. DESIGN: Here, we describe a procedure for preparing RNA-Seq libraries from 1 ...


Edaxadiene: A New Bioactive Diterpene From Mycobacterium Tuberculosis, Francis M. Mann, Meimei Xu, Xiaoming Chen, D. Bruce Fulton, David G. Russell, Reuben J. Peters 2017 Iowa State University

Edaxadiene: A New Bioactive Diterpene From Mycobacterium Tuberculosis, Francis M. Mann, Meimei Xu, Xiaoming Chen, D. Bruce Fulton, David G. Russell, Reuben J. Peters

Reuben J. Peters

Mycobacterium tuberculosis remains a widespread and devastating human pathogen. Presented here is the characterization of an atypical class I diterpene cyclase from M. tuberculosis that catalyzes an unusual cyclization reaction in converting the known M. tuberculosis metabolite halimadienyl diphosphate to a further cyclized novel diterpene, which we have termed edaxadiene, as it directly inhibits maturation of the phagosomal compartment in which the bacterium is taken up during infection.


Increasing Diterpene Yield With A Modular Metabolic Engineering System In E. Coli: Comparison Of Mev And Mep Isoprenoid Precursor Pathway Engineering, Dana Morrone, Luke Lowry, Mara K. Determan, David M. Hershey, Meimei Xu, Reuben J. Peters 2017 Iowa State University

Increasing Diterpene Yield With A Modular Metabolic Engineering System In E. Coli: Comparison Of Mev And Mep Isoprenoid Precursor Pathway Engineering, Dana Morrone, Luke Lowry, Mara K. Determan, David M. Hershey, Meimei Xu, Reuben J. Peters

Reuben J. Peters

Engineering biosynthetic pathways in heterologous microbial host organisms offers an elegant approach to pathway elucidation via the incorporation of putative biosynthetic enzymes and characterization of resulting novel metabolites. Our previous work in Escherichia coli demonstrated the feasibility of a facile modular approach to engineering the production of labdane-related diterpene (20 carbon) natural products. However, yield was limited (<0.1 mg/L), presumably due to reliance on endogenous production of the isoprenoid precursors dimethylallyl diphosphate and isopentenyl diphosphate. Here, we report incorporation of either a heterologous mevalonate pathway (MEV) or enhancement of the endogenous methyl erythritol phosphate pathway (MEP) with our modular metabolic engineering system. With MEP pathway enhancement, it was found that pyruvate supplementation of rich media and simultaneous overexpression of three genes (idi, dxs, and dxr) resulted in the greatest increase in diterpene yield, indicating distributed metabolic control within this pathway. Incorporation of a heterologous MEV pathway in bioreactor grown cultures resulted in significantly higher yields than MEP pathway enhancement. We have established suitable growth conditions for diterpene production levels ranging from 10 to >100 mg/L of E. coli culture. These amounts are sufficient for nuclear magnetic resonance analyses, enabling characterization of enzymatic products and hence, pathway elucidation. Furthermore, these results represent an up to >1,000-fold improvement in diterpene production from our facile, modular platform ...


Molecular Mechanisms Of Mycoplasma Hyopneumoniae Adherence To Swine Respiratory Epithelial Cells, Qijing Zhang 2017 Iowa State University

Molecular Mechanisms Of Mycoplasma Hyopneumoniae Adherence To Swine Respiratory Epithelial Cells, Qijing Zhang

Qijing Zhang

A microtiter plate adherence assay for Mycoplasma hyopneumoniae was established by using purified swine tracheal cilia which are the natural targets for the mycoplasma. M. hyopneumoniae bound specifically to solubilized cilia immobilized onto microtiter plates. Dextran sulfate, heparin, chondroitin sulfate, laminin, mucin, and fucoidan significantly inhibited binding of the mycoplasmas to cilia. Heparin, mucin, fucoidan, and chondroitin sulfate interacted with the adhesins on the surface of mycoplasmas, whereas laminin blocked the receptors in cilia. Treatment of cilia with neuraminidase appeared to promote adherence of the mycoplasmas; whereas, treatment of cilia with sodium metaperiodate decreased the binding. In the second study ...


Safety And Potential Efficacy Of Gemfibrozil As A Supportive Treatment For Children With Late Infantile Neuronal Ceroid Lipofuscinosis And Other Lipid Storage Disorders., Kyeongsoon Kim, Hynda K Kleinman, Hahn-Jun Lee, Kalipada Pahan 2017 George Washington University

Safety And Potential Efficacy Of Gemfibrozil As A Supportive Treatment For Children With Late Infantile Neuronal Ceroid Lipofuscinosis And Other Lipid Storage Disorders., Kyeongsoon Kim, Hynda K Kleinman, Hahn-Jun Lee, Kalipada Pahan

Biochemistry and Molecular Medicine Faculty Publications

Neuronal Ceroid Lipofuscinosis (NCL), also known as Batten disease, is a group of genetically distinct lysosomal disorders that mainly affect the central nervous system, resulting in progressive motor and cognitive decline primarily in children. Multiple distinct genes involved in the metabolism of lipids have been identified to date with various mutations in this family of diseases. There is no cure for these diseases but some new therapeutic approaches have been tested that offer more hope than the standard palliative care. Many of the therapeutic advances require invasive procedures but some progress in slowing the disease has been found and more ...


Insights Into Diterpene Cyclization From Structure Of Bifunctional Abietadiene Synthase From Abies Grandis, Ke Zhou, Yang Gao, Julie A. Hoy, Francis M. Mann, Richard B. Honzatko, Reuben J. Peters 2017 Iowa State University

Insights Into Diterpene Cyclization From Structure Of Bifunctional Abietadiene Synthase From Abies Grandis, Ke Zhou, Yang Gao, Julie A. Hoy, Francis M. Mann, Richard B. Honzatko, Reuben J. Peters

Reuben J. Peters

Abietadiene synthase from Abies grandis (AgAS) is a model system for diterpene synthase activity, catalyzing class I (ionization-initiated) and class II (protonation-initiated) cyclization reactions. Reported here is the crystal structure of AgAS at 2.3 Å resolution and molecular dynamics simulations of that structure with and without active site ligands. AgAS has three domains (α, β, and γ). The class I active site is within the C-terminal α domain, and the class II active site is between the N-terminal γ and β domains. The domain organization resembles that of monofunctional diterpene synthases and is consistent with proposed evolutionary origins of ...


Isotuberculosinol: The Unusual Case Of An Immunomodulatory Diterpenoid From Mycobacterium Tuberculosis, Francis M. Mann, Reuben J. Peters 2017 Winona State University

Isotuberculosinol: The Unusual Case Of An Immunomodulatory Diterpenoid From Mycobacterium Tuberculosis, Francis M. Mann, Reuben J. Peters

Reuben J. Peters

The actinomycetes family of bacteria is classically considered a rich source of natural products [1]. It is often suggested that such compounds have been selected by evolution to have biological activity [2]. For example, given the microbial-rich soil environment of the actinomycetes native habitat, their natural products have been suggested to serve in chemical warfare and/or signaling, which has been further connected to their leading role in providing pharmaceutically relevant antibiotic agents [3]. Nevertheless, surprisingly few of these molecules have been definitively assigned specific physiological roles in the native producing bacteria.


Structure And Mechanism Of The Diterpene Cyclase Ent-Copalyl Diphosphate Synthase, Mustafa Köksal, Huayou Hu, Robert M. Coates, Reuben J. Peters, David D. Christianson 2017 University of Pennsylvania

Structure And Mechanism Of The Diterpene Cyclase Ent-Copalyl Diphosphate Synthase, Mustafa Köksal, Huayou Hu, Robert M. Coates, Reuben J. Peters, David D. Christianson

Reuben J. Peters

The structure of ent-copalyl diphosphate synthase (CPS) reveals three α-helical domains (α, β, γ), as also observed in the related diterpene cyclase taxadiene synthase. However, active sites are located at the interface of the βγ domains in CPS but exclusively in the α domain of taxadiene synthase. Modular domain architecture in plant diterpene cyclases enables the evolution of alternative active sites and chemical strategies for catalyzing isoprenoid cyclization reactions.


Terpenoid Synthase Structures: A So Far Incomplete View Of Complex Catalysis, Yang Gao, Richard B. Honzatko, Reuben J. Peters 2017 Iowa State University

Terpenoid Synthase Structures: A So Far Incomplete View Of Complex Catalysis, Yang Gao, Richard B. Honzatko, Reuben J. Peters

Reuben J. Peters

The complexity of terpenoid natural products has drawn significant interest, particularly since their common (poly)isoprenyl origins were discovered. Notably, much of this complexity is derived from the highly variable cyclized and/or rearranged nature of the observed hydrocarbon skeletal structures. Indeed, at least in some cases it is difficult to immediately recognize their derivation from poly-isoprenyl precursors. Nevertheless, these diverse structures are formed by sequential elongation to acyclic precursors, most often with subsequent cyclization and/or rearrangement. Strikingly, the reactions used to assemble and diversify terpenoid backbones share a common carbocationic driven mechanism, although the means by which the ...


Two Rings In Them All: The Labdane-Related Diterpenoids, Reuben J. Peters 2017 Iowa State University

Two Rings In Them All: The Labdane-Related Diterpenoids, Reuben J. Peters

Reuben J. Peters

In his original exposition of the biogenetic isoprenoid rule, L. Ruzicka noted the structural identity between the fused A/B rings of triterpenoids/sterols and certain multicyclic diterpenoids as part of the impetus leading to that profound insight. His prescient hypothesis that this chemical structure relationship reflects similarities in the initial cyclization of these diterpenoids with that occurring in triterpenoid biosynthesis has since been verified. However, this chemical structure relationship does not continue to hold true for the additional rings found in many of these di- and tri- terpenoid natural products. This is now appreciated to arise from differences in ...


Functional Characterization Of Wheat Copalyl Diphosphate Synthases Sheds Light On The Early Evolution Of Labdane-Related Diterpenoid Metabolism In The Cereals, Yisheng Wu, Ke Zhou, Tomonobu Toyomasu, Chizu Sugawara, Madoka Oku, Shiho Abe, Masami Usui, Wataru Mitsuhashi, Makiko Chono, Peter M. Chandler, Reuben J. Peters 2017 Iowa State University

Functional Characterization Of Wheat Copalyl Diphosphate Synthases Sheds Light On The Early Evolution Of Labdane-Related Diterpenoid Metabolism In The Cereals, Yisheng Wu, Ke Zhou, Tomonobu Toyomasu, Chizu Sugawara, Madoka Oku, Shiho Abe, Masami Usui, Wataru Mitsuhashi, Makiko Chono, Peter M. Chandler, Reuben J. Peters

Reuben J. Peters

Two of the most agriculturally important cereal crop plants are wheat (Triticum aestivum) and rice (Oryza sativa). Rice has been shown to produce a number of diterpenoid natural products as phytoalexins and/or allelochemicals – specifically, labdane-related diterpenoids, whose biosynthesis proceeds via formation of an eponymous labdadienyl/copalyl diphosphate (CPP) intermediate (e.g., the ent-CPP of gibberellin phytohormone biosynthesis). Similar to rice, wheat encodes a number of CPP synthases (CPS), and the three CPS characterized to date (TaCPS1,2,&3) all have been suggested to produce ent-CPP. However, several of the downstream diterpene synthases will only react with CPP intermediate of normal or syn, but not ent, stereochemistry, as described in the accompanying report. Investigation of additional CPS did not resolve this issue, as the only other functional synthase (TaCPS4) also produced ent-CPP. Chiral product characterization of all the TaCPS then revealed that TaCPS2 uniquely produces normal, rather than ent-, CPP; thus, providing a suitable substrate source for the downstream diterpene synthases. Notably, TaCPS2 is most homologous to the similarly stereochemically differentiated syn-CPP ...


A Single Residue Switch For Mg2+-Dependent Inhibition Characterizes Plant Class Ii Diterpene Cyclases From Primary And Secondary Metabolism, Francis M. Mann, Sladjana Prisic, Emily K. Davenport, Mara K. Determan, Robert M. Coates, Reuben J. Peters 2017 Iowa State University

A Single Residue Switch For Mg2+-Dependent Inhibition Characterizes Plant Class Ii Diterpene Cyclases From Primary And Secondary Metabolism, Francis M. Mann, Sladjana Prisic, Emily K. Davenport, Mara K. Determan, Robert M. Coates, Reuben J. Peters

Reuben J. Peters

Class II diterpene cyclases mediate the acid-initiated cycloisomerization reaction that serves as the committed step in biosynthesis of the large class of labdane-related diterpenoid natural products, which includes the important gibberellin plant hormones. Intriguingly, these enzymes are differentially susceptible to inhibition by their Mg2+ cofactor, with those involved in gibberellin biosynthesis being more sensitive to such inhibition than those devoted to secondary metabolism, which presumably limits flux toward the potent gibberellin phytohormones. Such inhibition has been suggested to arise from intrasteric Mg2+ binding to the DXDD motif that cooperatively acts as the catalytic acid, whose affinity must then be modulated ...


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