King, Gavin W. (2009) Investigating helix-helix interactions in the transmembrane domains of membrane proteins. PhD thesis, University of Warwick.

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Abstract

Helix-helix interactions between membrane-spanning transmembrane (TM)
domains have been shown to drive the assembly of α-helical membrane proteins
within biological membranes. However, the rules that determine these interactions
are not yet fully understood, despite such interactions being found in an increasing
number of proteins. Recent work has implicated TM domain interactions in the
formation of the protein complex Ii-MHC, formed from the association of Major
Histocompatibility Complex Class II (MHC) and the MHC-associated-Invariant
Chain (Ii) proteins. Following biosynthesis, three MHC α/βheterodimers bind to
the Ii homotrimer to form a nonameric Ii-MHC complex within the endoplasmic
reticulum. This is a critical step in the export of MHC molecules to the antigen
presentation system and hence the activation of an immune response to a
pathogen. In this study we have explored the TM domain interactions within the
Ii-MHC complex. Results from in vivo and in vitro experiments revealed the TM
domains of the α- and β-chains of MHC have a propensity to self-associate into
homo-dimers and to associate with one another to form hetero-dimers. Highly
conserved GxxxG motifs (known to drive dimerization) were implicated in these
interactions. The TM domain of Ii was confirmed to self-associate to form trimers
by in vivo and in vitro methods, but surprisingly also displayed additional
oligomeric states suggesting the interaction is not as specific as was previously
thought. Furthermore, we show that in vivo, the TM domain of Ii can associate
with those of the α- and β-chains of MHC, whilst in vitro methods suggested Ii
preferentially binds to α-chains. Collectively, these findings strongly suggest that
the TM domains of Ii and MHC have a role to play in the assembly of the Ii-MHC
complex, and hence the very important process of antigen presentation.
Additionally, in this study we have undertaken development of NMR
spectroscopy methods that have the potential to increase our understanding of not
only the Ii-MHC complex, but protein-protein interactions in general.

Item Type:	Thesis (PhD)
Subjects:	Q Science > QP Physiology
Library of Congress Subject Headings (LCSH):	Biological transport -- Regulation, Membrane proteins -- Research, Protein-protein interactions -- Research
Official Date:	December 2009
Dates:	Date Event December 2009 Submitted
Institution:	University of Warwick
Theses Department:	Department of Chemistry
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Dixon, Ann M.
Sponsors:	Engineering and Physical Sciences Research Council (Great Britain) (EPSRC)
Format of File:	pdf
Extent:	190 leaves : ill., charts
Language:	eng

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