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Structure-function analysis of HAMLET (human alpha-lactalbumin made lethal to tumor cells)

Pettersson, Jenny LU (2007) In Lund University, Faculty of Medicine Doctoral Dissertation Series 2007:168
Abstract
The human genome sequence encodes fewer proteins than expected, suggesting that one protein can have several functions and adjust their structure to meet different structural demands. Changes in tertiary structure have mostly been associated with disease and the most striking example is the prion protein, which changes from a mixed alpha-helical and beta-sheet conformation to the beta-sheet rich, disease causing iso-form. Protein folding is becoming recognised as a mechanism to generate beneficial functional diversity, however. One example is alpha-lactalbumin, which by unfolding forms a tumoricidal complex with oleic acid called human alpha-lactalbumin made lethal to tumor cells (HAMLET), which kills tumor cells.



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The human genome sequence encodes fewer proteins than expected, suggesting that one protein can have several functions and adjust their structure to meet different structural demands. Changes in tertiary structure have mostly been associated with disease and the most striking example is the prion protein, which changes from a mixed alpha-helical and beta-sheet conformation to the beta-sheet rich, disease causing iso-form. Protein folding is becoming recognised as a mechanism to generate beneficial functional diversity, however. One example is alpha-lactalbumin, which by unfolding forms a tumoricidal complex with oleic acid called human alpha-lactalbumin made lethal to tumor cells (HAMLET), which kills tumor cells.



We investigated how protein sequence variation influences the formation of HAMLET, by comparing human, bovine, equine, caprine and porcine alpha-lactalbumin (paper I). The fatty acid specificity in HAMLET was studied using fatty acids differing in chain lenth, saturation and orientation of the double bond (paper II). We have also used stably unfolded alpha-lactalbumin mutants (paper III) to exclude effects of the native protein in tumor cells. In an attempt to determine the three-dimensional structure of HAMLET (paper IV) crystals were characterised by X-ray diffraction at 1.8 Å resolution. The unit cell differed significantly from native alpha-lactalbumin, confirming that the protein had undergone major structural alterations to form HAMLET.



These studies have added significantly to our understanding of HAMLET as a tumoricidal molecular complex. It is possible that HAMLET is only one of many beneficial protein-folding variants waiting to be discovered. (Less)
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author
supervisor
opponent
  • Prof Kuwajima, Kunihiro, National Institute of Natural Sciences, Okazaki, Japan
organization
publishing date
type
Thesis
publication status
published
subject
keywords
alpha-lactalbumin HAMLET oleic acid protein folding tumor cell death
in
Lund University, Faculty of Medicine Doctoral Dissertation Series 2007:168
pages
109 pages
publisher
Division of Microbiology, Immunology and Glycobiology - MIG
defense location
Segerfalksalen, Sölvegatan 17, Lund
defense date
2007-12-13 13:00
ISSN
1652-8220
ISBN
978-91-85897-46-9
language
English
LU publication?
yes
id
b7b7581a-251b-40ff-bbfa-855020a12085 (old id 605254)
date added to LUP
2007-11-20 13:48:42
date last changed
2016-09-19 08:44:57
@phdthesis{b7b7581a-251b-40ff-bbfa-855020a12085,
  abstract     = {The human genome sequence encodes fewer proteins than expected, suggesting that one protein can have several functions and adjust their structure to meet different structural demands. Changes in tertiary structure have mostly been associated with disease and the most striking example is the prion protein, which changes from a mixed alpha-helical and beta-sheet conformation to the beta-sheet rich, disease causing iso-form. Protein folding is becoming recognised as a mechanism to generate beneficial functional diversity, however. One example is alpha-lactalbumin, which by unfolding forms a tumoricidal complex with oleic acid called human alpha-lactalbumin made lethal to tumor cells (HAMLET), which kills tumor cells. <br/><br>
<br/><br>
We investigated how protein sequence variation influences the formation of HAMLET, by comparing human, bovine, equine, caprine and porcine alpha-lactalbumin (paper I). The fatty acid specificity in HAMLET was studied using fatty acids differing in chain lenth, saturation and orientation of the double bond (paper II). We have also used stably unfolded alpha-lactalbumin mutants (paper III) to exclude effects of the native protein in tumor cells. In an attempt to determine the three-dimensional structure of HAMLET (paper IV) crystals were characterised by X-ray diffraction at 1.8 Å resolution. The unit cell differed significantly from native alpha-lactalbumin, confirming that the protein had undergone major structural alterations to form HAMLET.<br/><br>
<br/><br>
These studies have added significantly to our understanding of HAMLET as a tumoricidal molecular complex. It is possible that HAMLET is only one of many beneficial protein-folding variants waiting to be discovered.},
  author       = {Pettersson, Jenny},
  isbn         = {978-91-85897-46-9},
  issn         = {1652-8220},
  keyword      = {alpha-lactalbumin HAMLET oleic acid protein folding tumor cell death},
  language     = {eng},
  pages        = {109},
  publisher    = {Division of Microbiology, Immunology and Glycobiology - MIG},
  school       = {Lund University},
  series       = {Lund University, Faculty of Medicine Doctoral Dissertation Series 2007:168},
  title        = {Structure-function analysis of HAMLET (human alpha-lactalbumin made lethal to tumor cells)},
  year         = {2007},
}