Biochemistry, Biophysics, and Structural Biology Commons^™

Structures Of Eccb1 And Eccd1 From The Core Complex Of The Mycobacterial Esx-1 Type Vii Secretion System, Jonathan Mark Wagner, Sum Chan, Timothy J. Evans, Sara Kahng, Jennifer Kim, Mark A. Arbing, David Eisenberg, Konstantin V. Korotkov

Molecular and Cellular Biochemistry Faculty Publications

Background: The ESX-1 type VII secretion system is an important determinant of virulence in pathogenic mycobacteria, including Mycobacterium tuberculosis. This complicated molecular machine secretes folded proteins through the mycobacterial cell envelope to subvert the host immune response. Despite its important role in disease very little is known about the molecular architecture of the ESX-1 secretion system.

Results: This study characterizes the structures of the soluble domains of two conserved core ESX-1 components – EccB₁ and EccD₁. The periplasmic domain of EccB₁ consists of 4 repeat domains and a central domain, which together form a quasi …

An Extended Polyanion Activation Surface In Insulin Degrading Enzyme, Eun Suk Song, Mehmet Ozbil, Tingting Zhang, Michael Sheetz, David Lee, Danny Tran, Sheng Li, Rajeev Prabhakar, Louis B. Hersh, David W. Rodgers

Molecular and Cellular Biochemistry Faculty Publications

Insulin degrading enzyme (IDE) is believed to be the major enzyme that metabolizes insulin and has been implicated in the degradation of a number of other bioactive peptides, including amyloid beta peptide (Aβ), glucagon, amylin, and atrial natriuretic peptide. IDE is activated toward some substrates by both peptides and polyanions/anions, possibly representing an important control mechanism and a potential therapeutic target. A binding site for the polyanion ATP has previously been defined crystallographically, but mutagenesis studies suggest that other polyanion binding modes likely exist on the same extended surface that forms one wall of the substrate-binding chamber. Here we use …

Transcriptional Activity Of The Islet Β Cell Factor Pdx1 Is Augmented By Lysine Methylation Catalyzed By The Methyltransferase Set7/9, Aarthi V. Maganti, Bernhard Maier, Sarah A. Tersey, Megan L. Sampley, Amber L. Mosley, Sabire Özcan, Boobalan Pachaiyappan, Patrick M. Woster, Chad S. Hunter, Roland Stein, Raghavendra G. Mirmira

Molecular and Cellular Biochemistry Faculty Publications

The transcription factor Pdx1 is crucial to islet β cell function and regulates target genes in part through interaction with coregulatory factors. Set7/9 is a Lys methyltransferase that interacts with Pdx1. Here we tested the hypothesis that Lys methylation of Pdx1 by Set7/9 augments Pdx1 transcriptional activity. Using mass spectrometry and mutational analysis of purified proteins, we found that Set7/9 methylates the N-terminal residues Lys-123 and Lys-131 of Pdx1. Methylation of these residues occurred only in the context of intact, full-length Pdx1, suggesting a specific requirement of secondary and/or tertiary structural elements for catalysis by Set7/9. Immunoprecipitation assays and mass …

Archaeal Nucleosome Positioning In Vivo And In Vitro Is Directed By Primary Sequence Motifs, Narasimharao Nalabothula, Liqun Xi, Sucharita Bhattacharyya, Jonathan Widom, Ji-Ping Wang, John N. Reeve, Thomas J. Santangelo, Yvonne N. Fondufe-Mittendorf

Molecular and Cellular Biochemistry Faculty Publications

Background: Histone wrapping of DNA into nucleosomes almost certainly evolved in the Archaea, and predates Eukaryotes. In Eukaryotes, nucleosome positioning plays a central role in regulating gene expression and is directed by primary sequence motifs that together form a nucleosome positioning code. The experiments reported were undertaken to determine if archaeal histone assembly conforms to the nucleosome positioning code.

Results: Eukaryotic nucleosome positioning is favored and directed by phased helical repeats of AA/TT/AT/TA and CC/GG/CG/GC dinucleotides, and disfavored by longer AT-rich oligonucleotides. Deep sequencing of genomic DNA protected from micrococcal nuclease digestion by assembly into archaeal nucleosomes has established that …

Pyrvinium Pamoate Changes Alternative Splicing Of The Serotonin Receptor 2c By Influencing Its Rna Structure, Manli Shen, Stanislav Bellaousov, Michael Hiller, Pierre De La Grange, Trevor O. Creamer, Orit Malina, Ruth Sperling, David H. Mathews, Peter Stoilov, Stefan Stamm

Molecular and Cellular Biochemistry Faculty Publications

The serotonin receptor 2C plays a central role in mood and appetite control. It undergoes pre-mRNA editing as well as alternative splicing. The RNA editing suggests that the pre-mRNA forms a stable secondary structure in vivo. To identify substances that promote alternative exons inclusion, we set up a high-throughput screen and identified pyrvinium pamoate as a drug-promoting exon inclusion without editing. Circular dichroism spectroscopy indicates that pyrvinium pamoate binds directly to the pre-mRNA and changes its structure. SHAPE (selective 2'-hydroxyl acylation analysed by primer extension) assays show that part of the regulated 5'-splice site forms intramolecular base pairs that …

Assembly Of The Type Ii Secretion System Such As Found In Vibrio Cholerae Depends On The Novel Pilotin Asps, Rhys A. Dunstan, Eva Heinz, Lakshmi C. Wijeyewickrema, Robert N. Pike, Anthony W. Purcell, Timothy J. Evans, Judyta Praszkier, Roy M. Robins-Browne, Richard A. Strugnell, Konstantin V. Korotkov, Trevor Lithgow

Molecular and Cellular Biochemistry Faculty Publications

The Type II Secretion System (T2SS) is a molecular machine that drives the secretion of fully-folded protein substrates across the bacterial outer membrane. A key element in the machinery is the secretin: an integral, multimeric outer membrane protein that forms the secretion pore. We show that three distinct forms of T2SSs can be distinguished based on the sequence characteristics of their secretin pores. Detailed comparative analysis of two of these, the Klebsiella-type and Vibrio-type, showed them to be further distinguished by the pilotin that mediates their transport and assembly into the outer membrane. We have determined the crystal structure of …

Fus-Nls/Transportin 1 Complex Structure Provides Insights Into The Nuclear Targeting Mechanism Of Fus And The Implications In Als, Chunyan Niu, Jiayu Zhang, Feng Gao, Liuqing Yang, Minze Jia, Haining Zhu, Weimin Gong

Molecular and Cellular Biochemistry Faculty Publications

The C-terminal nuclear localization sequence of FUsed in Sarcoma (FUS-NLS) is critical for its nuclear import mediated by transportin (Trn1). Familial amyotrophic lateral sclerosis (ALS) related mutations are clustered in FUS-NLS. We report here the structural, biochemical and cell biological characterization of the FUS-NLS and its clinical implications. The crystal structure of the FUS-NLS/Trn1 complex shows extensive contacts between the two proteins and a unique α-helical structure in the FUS-NLS. The binding affinity between Trn1 and FUS-NLS (wide-type and 12 ALS-associated mutants) was determined. As compared to the wide-type FUS-NLS (K(D) = 1.7 nM), each ALS-associated mutation caused a decreased …

Lafora Disease E3-Ubiquitin Ligase Malin Is Related To Trim32 At Both The Phylogenetic And Functional Level, Carlos Romá-Mateo, Daniel Moreno, Santiago Vernia, Teresa Rubio, Travis M. Bridges, Matthew S. Gentry, Pascual Sanz

Molecular and Cellular Biochemistry Faculty Publications

BACKGROUND: Malin is an E3-ubiquitin ligase that is mutated in Lafora disease, a fatal form of progressive myoclonus epilepsy. In order to perform its function, malin forms a functional complex with laforin, a glucan phosphatase that facilitates targeting of malin to its corresponding substrates. While laforin phylogeny has been studied, there are no data on the evolutionary lineage of malin.

RESULTS: After an extensive search for malin orthologs, we found that malin is present in all vertebrate species and a cephalochordate, in contrast with the broader species distribution previously reported for laforin. These data suggest that in addition to forming …

Conservation Of The Glucan Phosphatase Laforin Is Linked To Rates Of Molecular Evolution And The Glucan Metabolism Of The Organism, Matthew S. Gentry, Rachel M. Pace

Molecular and Cellular Biochemistry Faculty Publications

BACKGROUND: Lafora disease (LD) is a fatal autosomal recessive neurodegenerative disease. A hallmark of LD is cytoplasmic accumulation of insoluble glucans, called Lafora bodies (LBs). Mutations in the gene encoding the phosphatase laforin account for approximately 50% of LD cases, and this gene is conserved in all vertebrates. We recently demonstrated that laforin is the founding member of a unique class of phosphatases that dephosphorylate glucans.

RESULTS: Herein, we identify laforin orthologs in a protist and two invertebrate genomes, and report that laforin is absent in the vast majority of protozoan genomes and it is lacking in all other invertebrate …

Pre-Mrna Secondary Structures Influence Exon Recognition, Michael Hiller, Zhaiyi Zhang, Rolf Backofen, Stefan Stamm

Molecular and Cellular Biochemistry Faculty Publications

The secondary structure of a pre-mRNA influences a number of processing steps including alternative splicing. Since most splicing regulatory proteins bind to single-stranded RNA, the sequestration of RNA into double strands could prevent their binding. Here, we analyzed the secondary structure context of experimentally determined splicing enhancer and silencer motifs in their natural pre-mRNA context. We found that these splicing motifs are significantly more single-stranded than controls. These findings were validated by transfection experiments, where the effect of enhancer or silencer motifs on exon skipping was much more pronounced in single-stranded conformation. We also found that the structural context of …

Evidence That Talin Alternative Splice Variants From Ciona Intestinalis Have Different Roles In Cell Adhesion, Richard H. Singiser, Richard O. Mccann

Molecular and Cellular Biochemistry Faculty Publications

BACKGROUND: Talins are large, modular cytoskeletal proteins found in animals and amoebozoans such as Dictyostelium discoideum. Since the identification of a second talin gene in vertebrates, it has become increasingly clear that vertebrate Talin1 and Talin2 have non-redundant roles as essential links between integrins and the actin cytoskeleton in distinct plasma membrane-associated adhesion complexes. The conserved C-terminal I/LWEQ module is important for talin function. This structural element mediates the interaction of talins with F-actin. The I/LWEQ module also targets mammalian Talin1 to focal adhesion complexes, which are dynamic multicomponent assemblies required for cell adhesion and cell motility. Although Talin1 is …