Integral membrane proteins perform a wide range of biological processes, including respiration, signal transduction and molecular transport. Structural information is necessary for a full understanding of the mechanisms by which integral membrane proteins work. Ferrous iron transporter protein B (FeoB) is an integral membrane protein of Escherichia coli which is considered to transport ferrous iron in to bacteria. But there are no definite proofs or clear indications of the precise mechanism of ferrous transport. By expressing and crystallizing the G-protein domain (FeoGP) and FeoB, it will be helpful to know about the iron transport system. In order to express FeoB and FeoGP, expression vector pFeoB (FeoB in pGEX-4T-1) and pFeoGP (FeoB in pGEX-4T-1) were made. FeoB and FeoGP proteins were expressed and purified. Using vapour diffusion method crystallization trials of FeoB and FeoGP were done. Crystals of FeoGP are observed and no crystal formation for FeoB. Native crystals of FeoGP diffracted to 2.2 ?? resolution, and mant-GMPPNP crystals to 2.6 ??. Preliminary data processing indicate space group P212121 for native crystals, with cell dimensions 46 x 119 x 146 ??. The data set is 100% complete, Rmerge 0.08, and I/ ?? 3.2.

1 v. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Microbiology and Immunology, 1992

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1988. / Vita. Abstract. Includes bibliographical references (leaves 51-60). Also available via the Internet.

Thesis (Ph. D.)--Georgia State University, 2007. / Title from file title page. Phang C. Tai, committee chair; John Houghton Parjit Kaur, Chung-Dar Lu, committee members. Electronic text (148 p. : ill. (some col.)) : digital, PDF file. Description based on contents viewed Dec. 7, 2007. Includes bibliographical references (p. 125-140).

<p>Stafylococcus aureus, Stafylococcus epidermidis, Escherichia coli, Streptococcus</p><p>pyogenes och Bacillus sp. är bakterier som förekommer i vår normalflora eller runt om i</p><p>vår omgivning. De är i de allra flesta fall harmlösa men kan orsaka sjukdom ifall de</p><p>hamnar i t.ex. sår eller kontaminerar mat. Vissa av dessa bakterier har även en tendens att</p><p>utveckla resistens mot antibiotika, infektioner orsakade av resistenta bakterier kan bli</p><p>allvarliga och väldigt svåra att behandla. Detta är det främsta skälet till varför vi har valt</p><p>att undersöka ifall de ovan nämnda bakterierna förkommer på avdelningen SET på</p><p>Halmstad högskola. För att kunna identifiera de bakterier vi fann använde vi oss av en rad</p><p>olika biokemiska tester och resistensbestämningen utfördes bl.a. med hjälp av en PCR</p><p>körning. Vi fann alla de bakterier vi sökte efter förutom S. pyogenes och ingen av de</p><p>funna visade på någon resistens mot antibiotika.</p>

The mechanisms of substrate recognition by regulatory proteases are not well understood. Presently, two opposing models have arisen to describe E. coil Lon's ability to discriminate between substrates: one suggests the N-terminus involvement while the second suggests the C-terminus involvement. In this project, the role of the C-terminal domain as it relates to the recognition of Lon's normal physiological substrates RcsA, an activator of colanic acid capsular polysaccharide, and SulA, an inhibitor of cell division, was addressed. Using site-directed mutagenesis, five mutations in Lon (R537G, E538A, GS40W, R542G, R542P) were isolated. Their phenotypic impact was either similar in character to wildtype Lon (R537G, E538A) or ��lon cells (G540W, R542G, R542P). The stabilization of both RcsA and SulA based on phenotypic assays and immunological detection of lon* strains (G540W, R542G, R542P) suggests the C-terminal domain may be involved in substrate degradation as opposed to discriminator activity. / Graduation date: 2002

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Les systèmes toxine-antitoxine (TA) bactériens ont été découverts il y a une vingtaine d’année sur les plasmides à bas nombre de copie. Ils sont composés de deux gènes organisés en opéron, l’un codant pour une toxine stable et l’autre pour une antitoxine instable capable de neutraliser l’effet de la toxine. Les systèmes TA sont fortement représentés au sein de l’ensemble des génomes bactériens. Ils se localisent aussi bien sur des éléments génétiques mobiles (plasmides, phages, transposons,…) que dans les chromosomes, ce qui suggère que le transfert horizontal de gènes participe à leur dissémination. Le système TA ccd du plasmide F d’Escherichia coli (ccdF) est composé de l’antitoxine CcdA et de la toxine CcdB. Le système ccdF contribue à la stabilité du plasmide F en tuant les bactéries-filles n’ayant pas reçu de copies plasmidiques lors de la division bactérienne (tuerie post-ségrégationelle). Au cours de ce travail, nous avons caractérisé un homologue du système toxine-antitoxine ccd du plasmide F (ccdF) qui se situe dans le chromosome de la souche pathogène E. coli O157:H7 EDL933 entre les gènes folA et apaH (ccdO157). Les systèmes ccdF et ccdO157 coexistent naturellement dans les souches d’E. coli O157:H7, le système ccdF se trouvant sur le plasmide pO157 qui dérive du plasmide F. Nos résultats montrent que l’antitoxine plasmidique CcdAF neutralise l’effet de la toxine chromosomique CcdBO157, tandis que l’antitoxine chromosomique CcdAO157 ne contrecarre pas la toxicité de la toxine plasmidique CcdBF. Nous avons également montré que le système ccdF cause une tuerie post-ségrégationelle, lorsqu’il est cloné dans un plasmide instable, dans une souche possédant le système chromosomique ccdO157. Le système ccdF est donc fonctionnel en présence de son homologue chromosomique. Le système ccdO157 est absent du chromosome de la souche de laboratoire E. coli K-12 MG1655, où une région intergénique de 77 pb sépare les gènes folA et apaH. Celle-ci contient une séquence cible pour la transposition. Nous avons étudié la distribution du système ccdO157 au sein de 523 souches d’E. coli représentatives de l’ensemble des sérogroupes décrits. Nos résultats montrent que le système ccdO157 est présent au sein de souches appartenant à 47 sérogroupes différents. Nos résultats mettent en évidence la diversité de la région intergénique folA-apaH d’E. coli. Celle-ci peut contenir gènes codant pour des protéines présentant de l’homologie avec des protéines d’espèce bactériennes éloignées d’E. coli ou d’organismes eucaryotes, ainsi qu’un élément génétique mobile, l’IS621, ce qui montre que le système ccdO157 a intégré le chromosome d’E. coli via le transfert horizontal de gènes.

Stafylococcus aureus, Stafylococcus epidermidis, Escherichia coli, Streptococcus pyogenes och Bacillus sp. är bakterier som förekommer i vår normalflora eller runt om i vår omgivning. De är i de allra flesta fall harmlösa men kan orsaka sjukdom ifall de hamnar i t.ex. sår eller kontaminerar mat. Vissa av dessa bakterier har även en tendens att utveckla resistens mot antibiotika, infektioner orsakade av resistenta bakterier kan bli allvarliga och väldigt svåra att behandla. Detta är det främsta skälet till varför vi har valt att undersöka ifall de ovan nämnda bakterierna förkommer på avdelningen SET på Halmstad högskola. För att kunna identifiera de bakterier vi fann använde vi oss av en rad olika biokemiska tester och resistensbestämningen utfördes bl.a. med hjälp av en PCR körning. Vi fann alla de bakterier vi sökte efter förutom S. pyogenes och ingen av de funna visade på någon resistens mot antibiotika.

Ribosomes are multicomponent macromolecular particles and are essential for the survival of cells in all organisms. The ribosome's universal function is to catalyze polypeptide synthesis through translation of mRNA transcripts. Ribosomes from Escherichia coli, eubacterial organisms, have a sedimentation coefficient of 70S and are composed of 30S and 50S ribonucleoprotein subunits. The small ribosomal subunit is an assembly of 21 different proteins and a 16S ribosomal RNA. Within the 16S rRNA there are a few short stretches of universally conserved sequences spanning positions 517-533, 1394-1408, and 1492-1506. Clear functions for these sequence zones have not yet been assigned. Here I report a kinetic analysis of these highly conserved regions in the 16S rRNA and within the 30S ribosomal subunits. Binding affinity was measured in experiments that were based on protection from nuclease 51 digestion of short oligodeoxynucleotides hybridized to the designated regions. DNAs hybridized to regions 1400 and 1500 show significant differences in the apparent dissociation constants when measured in 30S particles as opposed to those found for 16S rRNA. Region 525 showed no difference in kinetic behavior. To further elucidate the functional and structural role played by the region centered about C1400 in 16S rRNA, a four nucleotide deletion was constructed within this region. The deletion was introduced by direct RNA manipulation using DNA/RNA hybridization, RNase H digestions, and ligation of the correct RNA fragments with T4 RNA ligase. I improved ligation efficiency of large RNA molecules by including a connector looped short DNA oligomer. Recycling products through phenyl boronate agarose (PBA-30) column also improved the efficiency of ligation. The mutagenized 16S rRNA fully reassembles into 30 particles and the altered 30S subunit possesses all of the normal ribosomal proteins. Altered ribosomes were functional in in vitro translation of MS2 mRNA. The altered ribosomes have lower translational activity relative to controls. Here I present indirect evidence suggesting that the decrease in the synthesis of MS2 coat proteins is the result of premature termination. The altered 16S RNA in ribosomes had an apparent dissociation constants with DNA probes comparable to those found for normal 16S rRNA. This suggest that the RNA is less flexible in the particle relative to normal 30S subunits. The deletion at 1400 did not have any effect on the physical properties of the 1500 region, as measured by DNA hybridization. A minor, but significant, effect on the 525 region was observed. A possible RNA/RNA interaction within the 30S particle is proposed to account for this observation. / Graduation date: 1992