Post-graduate theses
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Identifier |
000326715 |
Title |
Ο ρόλος της στροφής και του μοτίβου της επτάδας στην αναδίπλωση και σταθερότητης πρωτεΐνης Rop |
Author
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Κυριαζίδης, Γιάννης
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Thesis advisor
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Κοκκινίδης, Μιχάλης
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Abstract |
Xe process of protein folding still remains one of the biggest problems of biology. Rop is a
small protein that has been extensively used as a model system to study the protein folding
problem. Rop is a homodimeric protein and its the paradigm of a canonical 4-α-helical bundle. Its
biological role involves the regulation of copy number of the ColE1 plasmids of E.coli. Rop
exhibits a characteristic pattern of hydrophobic and polar residues (heptad pattern), which is
typical for 4-α-helical bundles, and it is disturbed only in the loop region. Despite the extensive
research, the precise nature of the role of the the loop region in protein folding still remains elusive.
Earlier studies indicate that the loop regions has a major role in determining the protein
structure, while in other cases a minor role of loops has been found. One single mutation of Ala to
proline (A31P), resulted in a complete reorganization of the protein topology. In order to clarify
the role of loop to the protein folding and in particular the role of the existence of the proline in
the loop, the double mutant αυτή D30GA31P was produced with the aim to study the eLect of
glycine in the loop region in the folding pathway of the protein which in the case of A31P was
leading to a molten-globule-like state.
Spectroscopic and thermodynamic studies were performed and the results suggest that this
mutant has a wt Rop-like structure i.e, which is diLerent from the A31P structure. Xis conYrms
the role of turn residues in the choice of folding pathway and the suggests that the eLects of the
loop region on the folding pathway are complex and both sequence- and position- dependent.
In this study, the design of the mutant Rop2aL is described , which aim restores the heptad
repeat at the turn region. In contrast to the Rop2a mutant, which has been previously studied and
showed very minor diLerences in structure according to wt-Rop, in Rop2aL replacing the residue
Q34 with a leucine restores also the hydrophobicity pattern present in of Rop2a. His-Rop2aL is
eluted from gel-Yltration chromatography in two diLerent populations, most likely one dimeric
and one tetrameric. It has been shown that under non-reductive conditions the tetrameric form is
favoured. Xe tetrameric populations show higher melting temperature compared to wt-Rop,
which may be due to a formation of a new more extensive hydrophobic core.
Crystals have been obtained for the case of RopD30GA31P and for the tetrameric
pupulations of Rop2aLin the presence and absense of β-mercaptoethanol. Structure determination
will reveal undoubtly the structural eLects observed in the above mutations.
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Physical description |
53 σ. : εικ. ; 30 εκ. |
Language |
Greek |
Issue date |
2008-04-07 |
Collection
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School/Department--School of Sciences and Engineering--Department of Biology--Post-graduate theses
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Type of Work--Post-graduate theses
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Permanent Link |
https://elocus.lib.uoc.gr//dlib/e/0/2/metadata-dlib-user1215415627-15387.tkl
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Views |
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