alpha-Lactalbumin unfolding is not sufficient to cause apoptosis, but is required for the conversion to HAMLET (human alpha-lactalbumin made lethal to tumor cells).
(2003) In Protein Science 12(12). p.2794-2804- Abstract
- HAMLET (human -lactalbumin made lethal to tumor cells) is a complex of human -lactalbumin and oleic acid (C18:1:9 cis) that kills tumor cells by an apoptosis-like mechanism. Previous studies have shown that a conformational change is required to form HAMLET from -lactalbumin, and that a partially unfolded conformation is maintained in the HAMLET complex. This study examined if unfolding of -lactalbumin is sufficient to induce cell death. We used the bovine -lactalbumin Ca2+ site mutant D87A, which is unable to bind Ca2+, and thus remains partially unfolded regardless of solvent conditions. The D87A mutant protein was found to be inactive in the apoptosis assay, but could readily be converted to a HAMLET-like complex in the presence of... (More)
- HAMLET (human -lactalbumin made lethal to tumor cells) is a complex of human -lactalbumin and oleic acid (C18:1:9 cis) that kills tumor cells by an apoptosis-like mechanism. Previous studies have shown that a conformational change is required to form HAMLET from -lactalbumin, and that a partially unfolded conformation is maintained in the HAMLET complex. This study examined if unfolding of -lactalbumin is sufficient to induce cell death. We used the bovine -lactalbumin Ca2+ site mutant D87A, which is unable to bind Ca2+, and thus remains partially unfolded regardless of solvent conditions. The D87A mutant protein was found to be inactive in the apoptosis assay, but could readily be converted to a HAMLET-like complex in the presence of oleic acid. BAMLET (bovine -lactalbumin made lethal to tumor cells) and D87A-BAMLET complexes were both able to kill tumor cells. This activity was independent of the Ca2+site, as HAMLET maintained a high affinity for Ca2+ but D87A-BAMLET was active with no Ca2+ bound. We conclude that partial unfolding of -lactalbumin is necessary but not sufficient to trigger cell death, and that the activity of HAMLET is defined both by the protein and the lipid cofactor. Furthermore, a functional Ca2+-binding site is not required for conversion of -lactalbumin to the active complex or to cause cell death. This suggests that the lipid cofactor stabilizes the altered fold without interfering with the Ca2+site. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/118791
- author
- Svensson, Malin LU ; Fast, Jonas LU ; Mossberg, Anki LU ; Düringer, Caroline LU ; Gustafsson, Lotta LU ; Hallgren, Oskar LU ; Brooks, Charles L. ; Berliner, Lawrence ; Linse, Sara LU and Svanborg, Catharina LU
- organization
- publishing date
- 2003
- type
- Contribution to journal
- publication status
- published
- subject
- in
- Protein Science
- volume
- 12
- issue
- 12
- pages
- 2794 - 2804
- publisher
- The Protein Society
- external identifiers
-
- wos:000186764600013
- pmid:14627739
- scopus:10744223979
- pmid:14627739
- ISSN
- 1469-896X
- DOI
- 10.1110/ps.0231003
- language
- English
- LU publication?
- yes
- id
- 5f5f6d98-011d-45d8-9728-f5a50aecaf3b (old id 118791)
- alternative location
- http://www.proteinscience.org/cgi/content/abstract/12/12/2794
- date added to LUP
- 2016-04-01 11:43:20
- date last changed
- 2022-01-26 17:17:36
@article{5f5f6d98-011d-45d8-9728-f5a50aecaf3b, abstract = {{HAMLET (human -lactalbumin made lethal to tumor cells) is a complex of human -lactalbumin and oleic acid (C18:1:9 cis) that kills tumor cells by an apoptosis-like mechanism. Previous studies have shown that a conformational change is required to form HAMLET from -lactalbumin, and that a partially unfolded conformation is maintained in the HAMLET complex. This study examined if unfolding of -lactalbumin is sufficient to induce cell death. We used the bovine -lactalbumin Ca2+ site mutant D87A, which is unable to bind Ca2+, and thus remains partially unfolded regardless of solvent conditions. The D87A mutant protein was found to be inactive in the apoptosis assay, but could readily be converted to a HAMLET-like complex in the presence of oleic acid. BAMLET (bovine -lactalbumin made lethal to tumor cells) and D87A-BAMLET complexes were both able to kill tumor cells. This activity was independent of the Ca2+site, as HAMLET maintained a high affinity for Ca2+ but D87A-BAMLET was active with no Ca2+ bound. We conclude that partial unfolding of -lactalbumin is necessary but not sufficient to trigger cell death, and that the activity of HAMLET is defined both by the protein and the lipid cofactor. Furthermore, a functional Ca2+-binding site is not required for conversion of -lactalbumin to the active complex or to cause cell death. This suggests that the lipid cofactor stabilizes the altered fold without interfering with the Ca2+site.}}, author = {{Svensson, Malin and Fast, Jonas and Mossberg, Anki and Düringer, Caroline and Gustafsson, Lotta and Hallgren, Oskar and Brooks, Charles L. and Berliner, Lawrence and Linse, Sara and Svanborg, Catharina}}, issn = {{1469-896X}}, language = {{eng}}, number = {{12}}, pages = {{2794--2804}}, publisher = {{The Protein Society}}, series = {{Protein Science}}, title = {{alpha-Lactalbumin unfolding is not sufficient to cause apoptosis, but is required for the conversion to HAMLET (human alpha-lactalbumin made lethal to tumor cells).}}, url = {{http://dx.doi.org/10.1110/ps.0231003}}, doi = {{10.1110/ps.0231003}}, volume = {{12}}, year = {{2003}}, }