title: Lipid modification gives rise to two distinct Haloferax volcanii S-layer glycoprotein populations.
abstract: The S-layer glycoprotein is the sole component of the protein shell surrounding Haloferax volcanii cells. The deduced amino acid sequence of the S-layer glycoprotein predicts the presence of a C-terminal membrane-spanning domain. However, several earlier observations, including the ability of EDTA to selectively solubilize the protein, are inconsistent with the presence of a trans-membrane sequence. In the present report, sequential solubilization of the S-layer glycoprotein by EDTA and then with detergent revealed the existence of two distinct populations of the S-layer glycoprotein. Whereas both S-layer glycoprotein populations underwent signal peptide cleavage and N-glycosylation, base hydrolysis followed by mass spectrometry revealed that a lipid, likely archaetidic acid, modified only the EDTA-solubilized version of the protein. These observations are consistent with the S-layer glycoprotein being initially synthesized as an integral membrane protein and subsequently undergoing a processing event in which the extracellular portion of the protein is separated from the membrane-spanning domain and transferred to a waiting lipid moiety.
authors.affiliation: Department of Life Sciences, Ben Gurion University of the Negev, Beersheva, Israel.
authors.forename: Lina
authors.initials: L
authors.lastname: Kandiba
authors.forename: Ziqiang
authors.initials: Z
authors.lastname: Guan
authors.forename: Jerry
authors.initials: J
authors.lastname: Eichler
mesh_terms: D019843:Archaeal Proteins / Q000378:metabolism; D001703:Biophysics / Q000379:methods; D002853:Chromatography, Liquid / Q000379:methods; D004492:Edetic Acid / Q000737:chemistry; D006023:Glycoproteins / Q000737:chemistry*; D006031:Glycosylation; D019622:Haloferax volcanii / Q000378:metabolism; D006868:Hydrolysis; D008055:Lipids / Q000737:chemistry*; D013058:Mass Spectrometry / Q000379:methods; D008562:Membrane Glycoproteins / Q000737:chemistry*; D021382:Protein Sorting Signals; D017434:Protein Structure, Tertiary; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods
chemical_list: D019843:Archaeal Proteins; D006023:Glycoproteins; D008055:Lipids; D008562:Membrane Glycoproteins; D021382:Protein Sorting Signals; C055764:S-layer proteins; D004492:Edetic Acid