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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Investigation of the assembly of TonA protein into the outer membrane of Escherichia coli

Jackson, Maria Elizabeth January 1984 (has links)
The majority of outer membrane, periplasmic and some inner membrane proteins of Escherichia coli are synthesised with signal sequences which initiate the translocation process. It has been suggested that other polypeptide sequences within the mature protein carry additional information which determines the final localisation of the product. The aim of this project was to investigate the assembly into the outer membrane of the E. coli ferrichrome receptor protein, TonA. The tonA gene was subcloned onto pBR325 in order to maximise expression of this normally minor outer membrane protein. A study of the kinetics of assembly of TonA in a strain harbouring a multicopy plasmid carrying tonA revealed the occurrence of a processed assembly intermediate which separated with the soluble (cytoplasmic plus periplasmic) fraction of sonicated cells. The position and direction of transcription of tonA was deduced by Tn1000 mutagenesis followed by analysis of the resultant truncated TonA' polypeptides synthesised in vitro and in maxicells. All the TonA' polypeptides thus produced, even those with apparently small C-terminal deletions, fractionated with the sarkosyl soluble envelope material in maxicells (wild type TonA is sarkosyl insoluble), suggesting an important role for the C-terminus in assembly. A similar result was obtained when the tonA gene was truncated using an "oligo-stop translation" sequence. This eliminated the possibility that complete assembly of the TonA' polypeptides truncated by Tn1000 insertion was prevented by Tn1000 encoded sequences at their C-termini. Synthesis of the hybrid MalE-LacZ protein, 72-47, was demonstrated to inhibit the processing of TonA and several inner membrane proteins. Since this hybrid was already known to block the assembly and processing of periplasmic and outer membrane proteins, this result suggests that all three classes of exported protein share common steps in their assembly.
2

Clathrin assemblies in vitreous ice : A structural analysis by image reconstruction

Vigers, G. P. A. January 1986 (has links)
No description available.
3

Structure and functional studies of the short consensus repeats of the human complement receptor type 1

Robinson, Joanne Claire January 2000 (has links)
No description available.
4

Molecular genetic analysis of the penicillin-binding protein 1B gene of Escherichia coli

Edelman, A. January 1987 (has links)
No description available.
5

Capping of the major rat thymocyte glycoproteins : Their interactions with other membrane proteins and the cytoskeleton

Turner, C. E. January 1986 (has links)
No description available.
6

Transmembrane Helix-Helix Interactions in a Bacterial Small Multidrug Transport Protein

Wang, Jun 11 December 2013 (has links)
EmrE from Escherichia coli is a member of the small multidrug resistance protein family that oligomerizes to export hydrophobic cationic antimicrobials by utilizing the proton motive force. We studied the helix-helix interactions of the four transmembrane (TM) segments of EmrE to determine how this protein might assemble into its oligomeric forms. Using a combination of biochemical and biophysical techniques, we assessed the oligomerization propensities of Lys-tagged EmrE TM peptides in membrane-mimetic environments. Our results established that each of the TMs of EmrE display detergent-sensitive self-association, but in particular, TM2 had the greatest dimerization capability that was not completely abolished even by scrambling the native sequence. Mutations made to TM2 in full-length EmrE also revealed that efflux-defective mutations are located on one face of the helix. These findings reveal another potential oligomerization site for EmrE - and perhaps SMRs - and may provide a target for development of novel efflux-inhibitors.
7

Transmembrane Helix-Helix Interactions in a Bacterial Small Multidrug Transport Protein

Wang, Jun 11 December 2013 (has links)
EmrE from Escherichia coli is a member of the small multidrug resistance protein family that oligomerizes to export hydrophobic cationic antimicrobials by utilizing the proton motive force. We studied the helix-helix interactions of the four transmembrane (TM) segments of EmrE to determine how this protein might assemble into its oligomeric forms. Using a combination of biochemical and biophysical techniques, we assessed the oligomerization propensities of Lys-tagged EmrE TM peptides in membrane-mimetic environments. Our results established that each of the TMs of EmrE display detergent-sensitive self-association, but in particular, TM2 had the greatest dimerization capability that was not completely abolished even by scrambling the native sequence. Mutations made to TM2 in full-length EmrE also revealed that efflux-defective mutations are located on one face of the helix. These findings reveal another potential oligomerization site for EmrE - and perhaps SMRs - and may provide a target for development of novel efflux-inhibitors.
8

Structure Investigations of Membrane Protein OEP16

January 2012 (has links)
abstract: Membrane protein structure is continuing to be a topic of interest across the scientific community. However, high resolution structural data of these proteins is difficult to obtain. The amino acid transport protein, Outer Envelope Protein, 16kDa (OEP16) is a transmembrane protein channel that allows the passive diffusion of amino acids across the outer chloroplast membrane, and is used as a model protein in order to establish methods that ultimately reveal structural details about membrane proteins using nuclear magnetic resonance (NMR) spectroscopy. Methods include recombinant expression of isotope enriched inclusion bodies, purification and reconstitution in detergent micelles, and pre-characterization techniques including circular dichroism (CD) spectroscopy, dynamic light scattering (DLS), and high pressure liquid chromatography (HPLC). High resolution NMR spectroscopy was able to assign 99% of the amide backbone and the chemical shifts provided detailed secondary structure of OEP16 on a per residue basis using the software TALOS+. Relaxation studies explored the intramolecular dynamics of OEP16 and results strongly support the resonance assignments. Successful titration studies were able to locate residues important for amino acid binding for import into the chloroplast as well as provide information on how the transmembrane helices of OEP16 are packed together. For the first time there is experimental evidence that can assign the location of secondary structure in OEP16 and creates a foundation for a future three dimensional structure. / Dissertation/Thesis / Ph.D. Biochemistry 2012
9

A Structural and Enzymatic Characterization of Purified Human Diacylglycerol Kinase Epsilon / Purification and Characterization of Diacylglycerol Kinase Epsilon

Jennings, William January 2016 (has links)
Diacylglycerol kinases (DGK’s) tightly regulate the intracellular levels of diacylglycerol (DAG) and phosphatidic acid (PA). DAG is an important intermediate in lipid biosynthetic pathways and acts as a lipid second messenger in a number of signaling pathways. Similarly, since PA serves as a potent signaling lipid and is a precursor for lipid biosynthesis, intracellular PA levels must be tightly regulated. There are ten isoforms of DGK in mammals, but we have decided to focus solely on the epsilon form (DGKε) in this work. DGKε is the only isoform that shows specificity for the acyl chains of its DAG substrate; as a consequence, it contributes to the dramatic enrichment of cellular lipids with sn-1 stearoyl and sn-2 arachidonoyl. The most notable example is the highly enriched bioactive lipid 1-stearoyl-2-arachidonoyl phosphatidylinositol. We have purified active human DGKε to near homogeneity and thoroughly characterized its stability as well as examined its secondary structure with CD. We also purified a truncated form (DGKε Δ40) that shows increased stability compared to the full-length protein. Our purified fractions are well suited for a wide range of exciting applications and studies. We have begun incorporating DGKε into liposomes in order to develop a liposome-based assay, which would be a dramatic improvement over the presently used micelle-based assay. This purification also allows for high throughput screens of chemical compounds to test for a specific inhibitor. These studies will reveal valuable information about the structural and functional properties of DGKε and will aid in the development of therapies for DGKε-related diseases. / Thesis / Master of Science (MSc)
10

Studies of the transmembrane domain of the human erythrocyte anion exchanger (band 3)

Young, Mark January 2000 (has links)
No description available.

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