Thesis (Ph. D.)--University of Wisconsin, 1965. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliography.

Göttingen, Univ., Diss., 2002. / Computerdatei im Fernzugriff.

Bielefeld, Univ., Diss., 2001. / Computerdatei im Fernzugriff.

Bielefeld, Univ., Diss., 2001. / Computerdatei im Fernzugriff.

Göttingen, Universiẗat, Diss., 2002.

Bielefeld, Universiẗat, Diss., 2001.

Thesis (Ph. D.)--University of Texas at Dallas, 2007. / Includes vita. Includes bibliographical references (leaves 191-192)

No description available.

Hydroxyproline (trans-4-hydroxy-L-proline (4-L-Hyp)) can be used by certain microorganisms as a source of carbon and nitrogen. The nitrogen fixing bacterium, Sinorhizobium meliloti carries a cluster (hyp cluster) of 14 genes responsible for the transport and degradation of this amino acid in the cell. The biological functions of several gene products in the hyp cluster are still unknown. So far, it is known that the conversion of trans-4-hydroxy-proline to α-ketoglutarate, one of the intermediate of the TCA cycle, occurs in four enzymatic reactions. The whole hyp cluster is up regulated in the presence of 4-hydroxy-proline in the media. Previous studies have shown several other 4-hydroxy-proline-inducible genes. One of these genes, smc04388, has been annotated as a putative omega amino transaminase. The role of this omega transaminase in the main catabolic pathway of 4-hydroxy-proline has not been investigated. In order to address this, two mutant strains; a single smc04388 mutant and a double smc04388 hypD mutant were created. Growth curves of these mutants in minimal media showed that the Smc04388 protein is not required for the growth of S. meliloti in the presence of trans-4-hydroxy-L-proline as the sole carbon and nitrogen source. The Smc04388 protein was overexpressed as a Strep-tagged and purified from S. meliloti. The purified enzyme showed amino transaminase activity with pyruvate and α-methylbenzylamine. In addition, an enzymatic reaction using the product of the second enzyme of the 4-hydroxy-proline pathway, Δ1-pyrroline-4-hydroxy-2-carboxylate, was carried out to test the activity of Smc04388 with this compound. Mass spectrometry analysis of this reaction mixture revealed the formation of L-alanine from pyruvate and Δ1-pyrroline-4-hydroxy-2-carboxylate, suggesting the utilization of this compound as an amino donor by the Smc04388 transaminase. It was also shown that transamination activity in cell extracts increase in the absence of Δ1-pyrroline-4-hydroxy-2-carboxylate deaminase, the enzyme that catalyzes the conversion of this compound in the 4-hydroxy-proline pathway. These results confirmed the hypothesis that the Smc04388 omega amino transaminase is involved in a secondary pathway related to the known catabolic pathway of 4-hydroxy-proline in bacteria. Further understanding of this secondary pathway will contribute to the study of the metabolism of 4-hydroxy-proline in bacteria. In addition to this, the complete characterization of the Smc04388 omega amino transaminase could have practical application in the pharmaceutical industry. / Thesis / Master of Science (MSc)

The genome of the a-proteobacterium Sinorhizobium meliloti has been completely sequenced and annotated. providing a wealth of information about this endosymbiotic N2 fixing organism. Although the structure of the genome, consisting of a circular chromosome and two smaller pSymA and pSymB replicons, has long been known, only a small portion of ORFs have previously been characterized. Sequence analysis of pSymB has revealed that a large portion of the 1570 ORFs code for solute uptake systems and polysaccharide biosynthesis. The pSymB replicon been referred to as a "megaplasmid," implying that pSymB is non-essential for viability of the organism. However, coded on pSymB are several essential genes, including a tRNA ArgCCG gene and the minCDE genes, which are not found elsewhere in the genome. Replication of pSymB is controlled by repABC genes, a typical property of plasmids among Rhizobiaceae. Therefore, the genome signature, a compositional analysis that allows comparison of whole replicons rather than focusing on particular genes, was used to provide support for designation of pSymB as a second chromosome in S. mdiloti. It was found that among a-proteobacteria, plasmids and chromosomes have distinctive patterns of dinucleotide biases, and in this respect, pSymB is chromosome-like while pSymA is plasmid-like. This brings into question how the pSymB replicon came to acquire chromosome-like properties while appearing to be maintained as a plasmid in the genome. Whole-genome nearest neighbor analysis shows that the linear chromosome of Agrobacterium tumefaciens and pSymB may have a common origin. Despite conservation of gene order within small groups of genes, it is evident that rearrangements, duplications, and horizontal transfer of genes since the divergence of these species have contributed to the mosaic nature of pSymB. Since synteny between the S. meliloti chromosome and A. tumefaciens circular chromosome is highly conserved, it appears that the instability of pSy mB has played a key role in the adaptation and evolution of S. meliloti. / Thesis / Master of Science (MS)