Étude structurale de protéines du bactériophage p2 par cristallographie aux rayons X et résonance magnétique nucléaire

Authors: Hamel, Jérémie
Advisor: Shi, RongGagné, Stéphane
Abstract: Cheese fermentation is a process in which milk is fermented by the Gram-positive bacteria Lactococcus lactis. However, the fermentation can be slowed or even stopped if specifi lactococcal bacteriophages are present in the medium. To this day, the infection mechanism of bacteriophages is still not fully known. The hijacking of the cell’s molecular machinery is carried out by proteins expressed by the phages’ early- and mid-expressed genes. The phage studied in this thesis is phage p2, of the Caudovirales order, Siphoviridae family and sk1-like group. The structure of phage p2 is known, but most early-and mid-expressed proteins do not have homologues of known structure or function in the public databases. These genes were cloned in a bacterial expression system in order to be expressed and the proteins purified and crystallized to determine their structure by X-ray crystallography. The protein encoded by the gene orf47 was commercially synthesized to be studied by nuclear magnetic resonance. Our overall goal is to suggest roles for these proteins by obtaining their structure and performing a structural homology query. Crystals were obtained for the proteins ORF-24, SaV (expressed from the gene orf26) and ORF-37 but more work is required in order to determine their structure. The structure of ORF-47 was obtained by nuclear magnetic resonance and has been found to have a fold highly similar to domains B, C and E of staphylococcal protein SpA. These domains bind human immunoglobulin G. The binding of similar proteins in L. lactis by ORF-47 has yet to be experimentally confirmed.
Document Type: Mémoire de maîtrise
Issue Date: 2017
Open Access Date: 31 October 2019
Permalink: http://hdl.handle.net/20.500.11794/37154
Grantor: Université Laval
Collection:Thèses et mémoires

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