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Title: Structural studies of Bacillus subtilis YqeN and Campylobacter jejuni Cj1289.
Author: Suwannachart, Chatrudee
ISNI:       0000 0004 2740 8305
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2011
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The YqeN protein from B. subtilis is believed to be one of the clamp loader subunits involved in assembly of the p-sliding clamp onto DNA during replication. It works together with the DnaX (τ) and HolB protein subunits. My 2.1 Å YqeN structure shows most structural similarity with 8 protein from E. coli even though the sequence identity between them is only 16 %. It reveals residues likely to be critical for l3-sliding clamp interaction. Attempts are also described here at crystallization of HolB and a DnaX(τ)NqeN/HolB complex. They were not successful but established a clear protocol for formation of a stable complex and also revealed the marked proteolytic sensitivity of DnaX. Results of HolB and DnaX (τ) structure prediction also confirmed the high structural similarity with the equivalent proteins from E. coli. Cj 1289 was formerly an uncharacterized protein from Campylobacter jejuni the food-borne pathogen. The 2.3 Å structure of Cj 1289 from my experiment showed structural homology to SurA chaperone protein from E. coli and some similarity to C. jejuni PEB4, which is a major antigenic virulence factor implicated in host cell adhesion, invasion and colonisation. The Cj 1289 structure showed clear similarity to the chaperone and PPlase domains of SurA and PEB4. However, Cj 1289 chaperone domain did not show activity in the rhodanese refolding and aggregation assays. It is possible that it requires a specific substrate which is related to its physiological role in the periplasm of C. jejuni. Moreover, purified Cj 1289 also enhanced RNAase TI refolding, although less active when compared with active protein such as PEB4. In addition, a drug inhibition experiment revealed that only juglone completely inhibits the Cjl289 PPlase activity. This also confirmed that the PPlase domain of Cjl289 has parvulin type folding.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available