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Title: Investigating the antimicrobial peptide resistance and mechanism of RosB and the Sap system
Author: Smith, Ryan Douglas
ISNI:       0000 0004 5993 1280
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 2016
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Bacteria have adapted to CAMP insult in many ways, this study has focused on two resistance mechanism for CAMPs, firstly the putatative potassium proton antiporter RosB has been shown not to efflux potassium with treatment of polymyxin B. The mechanism of resistance of RosB in Yersinia enterococcus was proposed to be a lowering of internal pH from a potassium efflux and a proton influx. The RosB homologue from Vibrio paraheamolyticus is able to efflux potassium with electrophile treatment, but unlike the potassium proton antiporter KefKC this potassium transport is not associated with CAMP resistance. The lack of resistance is likely to be due to an absence of intracellular pH regulation seen with the Vibrio RosB. The RosB homologue from E. coli YbaL has been shown to increase resistance to the electrophile NEM in high potassium media, but YbaL does not transport potassium when NEM is present. This suggests that YbaL is transporting another ion. The mechanism of ion transport for RosB is based on the sodium antiporter NhaA and NapA, this is due to similarities in the ion selection motif. There are differences between the Vibrio and Yersina homologue which would suggest that the Yersinia homologue is not transporting potassium. This second CAMP resistance mechanism studied was the ABC transporter Sap, with the focus of work done on the periplasmic substrate binding protein SapA. SapA binds the peptide within the periplasm and delivers it to the membrane domain for uptake in to the cell. It was not possible to detect any peptide binding to the SapA homologues from Klebsiella pneumonia or E. coli. Finally CAMPs purification was attempted under taken through Ni-NTA and chitin chromatography to produce human antimicrobial peptides. It was possible to 12 produce the human antimicrobial peptide HBD2 with thioredoxin fusion complex via Ni-NTA chromatography.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Peptides ; Potassium