Jenei, Zsuzsanna (2010) Transmembrane domain interactions in carnitine palmitoyltransferase I. PhD thesis, University of Warwick.

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Abstract

Membrane proteins are involved in a wide range of vital cellular processes,
responsible for relaying signals and cargo across cell membranes. A deeper
molecular understanding of their function is essential to elucidate the mechanisms of
numerous diseases and medical conditions. As an example, the carnitine
palmitoyltransferase 1 (CPT1) enzymes are responsible for the regulation of
mitochondrial fatty acid oxidation thus are central to cell function.
Previous work had shown that the transmembrane (TM) domains of the mitochondrial
outer membrane protein CPT1 have a significant influence on the enzyme’s kinetics,
which is different in the two catalytically active isoforms, CPT1A and CPT1B. It was
also shown that TM-domains, and specifically TM2, are involved in driving the
oligomerisation of the full length CPT1A. For this reason, the study of TM-TM
oligomerisation and their roles in the function of CPT1 are fundamentally important in
the design of pharmacological strategies aimed at the modulation of the activities of
these enzymes in conditions such as diabetes.
The main focus of this PhD research was to systematically investigate the homo- and
hetero-oligomerisation of the TM domains to help better understand the structurefunction
relationship for CPT1 membrane proteins. In this project, different
techniques were used from the areas of chemistry, molecular biology, and biophysics
(in vivo oligomerisation assays, chemical crosslinking, circular dichroism and
analytical ultracentrifugation), in order to examine these interactions.
The membrane spanning sequences of rCPT1A and rCPT1B were found to selfassociate,
and the order of oligomerisation was also determined. Sequence motifs
likely to be responsible for the interactions of these TM domains were identified using
in silico modelling. Mutagenesis analyses confirmed the role of suggested GxxxG(A)
motifs in the homo-oligomerisation of rCPT1A TM2 domains. The heterooligomerisation
of TM1-TM2 domains was also studied, and was found to be
significant in both isoforms. The work presented in this thesis shows that the
membrane spanning regions of the CPT1 enzymes are capable of interacting through
both homo- and hetero-oligomerisation. The results strongly suggest that these
interactions may play a significant role in the complex formation of the full length
enzymes and provide further evidence that CPT1 may function as a channel in the
outer mitochondrial membrane.

Item Type:	Thesis or Dissertation (PhD)
Subjects:	Q Science > QD Chemistry Q Science > QP Physiology
Library of Congress Subject Headings (LCSH):	Membrane proteins, Carnitine, Transferases
Official Date:	February 2010
Dates:	Date Event February 2010 Submitted
Institution:	University of Warwick
Theses Department:	Department of Chemistry
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Dixon, Ann
Sponsors:	University of Warwick
Extent:	xiii, 140, A5 leaves : ill., charts
Language:	eng

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