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Eukaryotic Cell, October 2009, p. 1567-1574, Vol. 8, No. 10
1535-9778/09/$08.00+0     doi:10.1128/EC.00136-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Dual Acylation Accounts for the Localization of {alpha}19-Giardin in the Ventral Flagellum Pair of Giardia lamblia{triangledown} ,{dagger}

Mirela Saric,1,{ddagger} Anke Vahrmann,1,{ddagger} Daniela Niebur,1 Verena Kluempers,1 Adrian B. Hehl,2 and Henning Scholze1*

Department of Biology/Chemistry, Biochemistry, University of Osnabrueck, D-49069 Osnabrueck, Germany,1 Institute of Parasitology, University of Zürich, CH-8057 Zürich, Switzerland2

Received 12 May 2009/ Accepted 6 August 2009

A Giardia-specific protein family denominated as {alpha}-giardins, represents the major protein component, besides tubulin, of the cytoskeleton of the human pathogenic parasite Giardia lamblia. One of its members, {alpha}19-giardin, carries an N-terminal sequence extension of MGCXXS, which in many proteins serves as a target for dual lipid conjugation: myristoylation at the glycine residue after removal of the methionine and palmitoylation at the cysteine residue. As the first experimental evidence of a lipid modification, we found {alpha}19-giardin to be associated with the membrane fraction of disrupted trophozoites. After heterologous coexpression of {alpha}19-giardin with giardial N-myristoyltransferase (NMT) in Escherichia coli, we found the protein in a myristoylated form. Additionally, after heterologous expression together with the palmitoyl transferase Pfa3 in Saccharomyces cerevisiae, {alpha}19-giardin associates with the membrane of the main vacuole. Immunocytochemical colocalization studies on wild-type Giardia trophozoites with tubulin provide evidence that {alpha}19-giardin exclusively localizes to the ventral pair of the giardial flagella. A mutant in which the putatively myristoylated N-terminal glycine residue was replaced by alanine lost this specific localization. Our findings suggest that the dual lipidation of {alpha}19-giardin is responsible for its specific flagellar localization.

* Corresponding author. Mailing address: Faculty of Biology/Chemistry, Barbarastrasse 13, D-49069 Osnabrueck, Germany. Phone: 49 541 9693423. Fax: 49 541 9692884. E-mail: scholze{at}biologie.uni-osnabrueck.de

{triangledown} Published ahead of print on 14 August 2009.

{dagger} Supplemental material for this article may be found at http://ec.asm.org/.

{ddagger} M.S. and A.V. contributed equally to this work.

Eukaryotic Cell, October 2009, p. 1567-1574, Vol. 8, No. 10
1535-9778/09/$08.00+0     doi:10.1128/EC.00136-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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