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Divergence of thioesterase function : human BFIT2, Escherichia coli EntH, and YDII


Please use this identifier to cite or link to this item: http://hdl.handle.net/1928/12073

Divergence of thioesterase function : human BFIT2, Escherichia coli EntH, and YDII

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Title: Divergence of thioesterase function : human BFIT2, Escherichia coli EntH, and YDII
Advisor(s): Dunaway-Mariano, Debra
Committee Member(s): Mariano, Patrick
Allen, Karen
Melancon, Charles
Department: University of New Mexico. Dept. of Chemistry
Subject: Function Hotdog Thioesterase
LC Subject(s): Esterases--Structure-activity relationships.
Thiolases--Structure-activity relationships.
Degree Level: Doctoral
Abstract: My doctoral research primarily focuses on two hotdog-fold thioesterases, EntH (also known as YbdB) from E. coli, and BFIT2 from Homo sapiens. The EntH (YbdB) gene is included in a large gene cluster that encodes the enzymes of the biosynthetic pathway leading to enterobactin. Building on the hypothesis that EntH might function in a “house-keeping” role by liberating misacylated EntB, two potential pathways to EntB misacylation were identified, one involving the phosphopantetheinyl transferase EntD and the other involving 2,3-DHB-AMP ligase EntE. EntH displays thioesterase activity towards a variety of acyl and aryl-holo EntB adducts. Lastly, It was shown that EntF acts on the 2,3-DHB-holo-EntB quickly, but not quickly on misacylated EntB adducts.tandem hotdog-fold thioesterase domains and a C-terminal steroidogenic acute regulatory protein related lipid transfer (START) domain. The expression of BFIT2 is induced during the thermogenesis transition of brown fat tissue. The expression of the recombinant BFIT2 in transfected HEK cells was confirmed by Western blot analysis. The recombinant BFIT2 contains a N-terminal His6-tag and epitope, which was found to be susceptible to posttranslational removal. The recombinant N-terminal (minus residues 1-34) truncated mutant was found not to undergo posttranslational cleavage, thus suggesting that the N-terminal region is a signal sequence. A chimeric protein BFIT2 N(1-42)-GFP was shown by confocal microscopy to co-locate with the mitochondria. The BFTI2 precursor was shown to be taken up by freshly isolated HEK cell mitochondria and cleaved to the mature form. These results confirmed that the N-terminal region of BFIT2 functions as MTS. During the thermogenesis transition of brown fat tissue, BFIT2 might function to restore the balance between free CoA and fatty acyl-CoA by hydrolyzing the long to medium chain fatty acyl-CoAs. Consistent with this hypothesis, BFIT2 was found to be much more active towards palmitoyl-CoA, myristoyl-CoA and lauroyl-CoA.
Graduation Date: December 2010
URI: http://hdl.handle.net/1928/12073

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