PIGF is a protein involved in the ethanolamine phosphate (EtNP) transfer steps of glycosylphosphatidylinositol (GPI) biosynthesis. PIGF forms a heterodimer with either PIGG or PIGO, two enzymes that transfer an EtNP to the second or third mannoses of GPI respectively. Heterodimer formation is essential for stable and regulated expression of PIGO and PIGG, but the functional significance of PIGF remains obscure. In the present study, we show that PIGF binds to PIGO and PIGG through distinct molecular domains. Strikingly, C-terminal half of PIGF was sufficient for its binding to PIGO and PIGG and yet this truncation mutant could not complement the PIGF defective mutant cells, suggesting that heterodimer formation is not sufficient for PIGF function. Furthermore, we identified a highly conserved motif in PIGF and demonstrated that the motif is not involved in binding to PIGO or PIGG, but critical for its function. Finally, we identified a PIGF homologue from Trypanosoma brucei and showed that it binds specifically to the T. brucei PIGO homologue. These data together support the notion that PIGF plays a critical and evolutionary conserved role in the ethanolamine-phosphate transfer-step, which cannot be explained by its previously ascribed binding/stabilizing function. Potential roles of PIGF in GPI biosynthesis are discussed.
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Research Article|
September 22 2014
New insights into the functions of PIGF, a protein involved in the ethanolamine phosphate transfer steps of glycosylphosphatidylinositol biosynthesis
Matthew J. Stokes;
Matthew J. Stokes
*Laboratory of Immunoglycobiology, WPI Immunology Frontier Research Center, Osaka University, Osaka 565-0871, Japan
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Yoshiko Murakami;
Yoshiko Murakami
*Laboratory of Immunoglycobiology, WPI Immunology Frontier Research Center, Osaka University, Osaka 565-0871, Japan
†Department of Immunoregulation, Research Institute for Microbial Diseases, Osaka University, Osaka 565-0871, Japan
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Yusuke Maeda;
Yusuke Maeda
*Laboratory of Immunoglycobiology, WPI Immunology Frontier Research Center, Osaka University, Osaka 565-0871, Japan
†Department of Immunoregulation, Research Institute for Microbial Diseases, Osaka University, Osaka 565-0871, Japan
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Taroh Kinoshita;
Taroh Kinoshita
*Laboratory of Immunoglycobiology, WPI Immunology Frontier Research Center, Osaka University, Osaka 565-0871, Japan
†Department of Immunoregulation, Research Institute for Microbial Diseases, Osaka University, Osaka 565-0871, Japan
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Yasu S. Morita
Yasu S. Morita
1
*Laboratory of Immunoglycobiology, WPI Immunology Frontier Research Center, Osaka University, Osaka 565-0871, Japan
†Department of Immunoregulation, Research Institute for Microbial Diseases, Osaka University, Osaka 565-0871, Japan
1To whom correspondence should be addressed at the present address: Department of Microbiology, University of Massachusetts, Amherst, MA 01003, U.S.A. (email ymorita@microbio.umass.edu).
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Publisher: Portland Press Ltd
Received:
April 28 2014
Revision Received:
July 25 2014
Accepted:
July 30 2014
Accepted Manuscript online:
July 30 2014
Online ISSN: 1470-8728
Print ISSN: 0264-6021
© The Authors Journal compilation © 2014 Biochemical Society
2014
Biochem J (2014) 463 (2): 249–256.
Article history
Received:
April 28 2014
Revision Received:
July 25 2014
Accepted:
July 30 2014
Accepted Manuscript online:
July 30 2014
Citation
Matthew J. Stokes, Yoshiko Murakami, Yusuke Maeda, Taroh Kinoshita, Yasu S. Morita; New insights into the functions of PIGF, a protein involved in the ethanolamine phosphate transfer steps of glycosylphosphatidylinositol biosynthesis. Biochem J 15 October 2014; 463 (2): 249–256. doi: https://doi.org/10.1042/BJ20140541
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