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Title: Granaticin : towards exploring the rare biosynthetic events of a double C-glycosylation
Author: Obasanjo, Oluwafunsho Abiodun
ISNI:       0000 0004 2717 9629
Awarding Body: University of East Anglia
Current Institution: University of East Anglia
Date of Award: 2011
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Pharmaceutically useful natural products such as the antibiotic erythromycin are often glycosylated. In many cases the glycosylation of natural products are often critical to their bioactivity. Therefore, advances in our understanding of the mechanism of glycosylation by glycosyltransferases are important. These glycosyltransferases could potentially be harnessed to allow rapid access to series of novel unnatural products of medical significance. The work described in this thesis focuses on the bi- and tri- functional glycosyltransferase; gra-14, involved in the formation of the two C-glycoside links in the granaticins and also of the O-glycoside link found in granaticin B and dihydrogranaticin B. A single C-glycoside link between a sugar moiety and its aglycone core is a common feature, in natural products isolated to date only the granaticin's exhibit two C-glycosidic bonds to a single sugar moiety. The glycosyltransferase was cloned from S. violaceoruber Tii22 and a revision of the sequence discovered which was supported by the recently deposited granaticin biosynthetic gene sequence from S. vietnamensis GIMV4.0001, after which overexpression and purification of the protein enabled the production of pure and homogenous recombinant Gra-14. The corresponding protein product was not capable of generating glycosylated products in vitro with variant substrates. The putative natural sugar donor TDP-4-keto-2,6-dideoxy-D-glucose was then reconstituted in both E. coli and S. lividans TK24, unfortunately it did not result in glycosylated derivates of the aglycones. These studies showed that the glycosyltransferase has stringent substrate specificity. Attempts at crystallisation were unsuccessful as the crystals of the glycosyltransferase obtained were not diffraction quality and hampered any attempts for structural and mechanistic studies.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available