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Title: Characterisation of OCR, the product of gene 0.3 from bacteriophage T7
Author: Atanasici, C.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2001
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The OCR protein of bacteriophage T7 is a small, dimeric protein which inhibits the cleavage of the phage DNA by type I restriction enzymes present in the infected host cell. I have studied the structure and the stability of OCR and analysed its binding to the EcoKI type I restriction-modification enzyme. OCR has an unique Tryptophan residue in position 94 which is solvent exposed and important for protein stability but not activity. The protein has a melting temperature of 72.19 °C and a molar extinction coefficient of 32095 M-1 cm-1. Asparagine 4 residue from one monomer is in close proximity to Asparagine 4 in the other monomer. Serine 68 residues are also at the monomer-monomer interface. Six surface exposed amino acids were substituted with cysteine and labelled with cysteine-specific fluorophores. The interaction between labelled OCR(Cys) proteins and EcoKI methylase revealed a huge surface area buried at the interface of the two proteins. OCR binds tightly to the R and S subunits of EcoKI and weakly to the M subunit of EcoKI. One OCR dimer binds to EcoKI methylase and two dimers to EcoKI nuclease. Both OCR-EcoKI methylase and OCR-EcoKI nuclease complexes have a Kd of about 10-11 M.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available