Lipid modification of proteins in Archaea: attachment of a mevalonic acid-based lipid moiety to the surface-layer glycoprotein of Haloferax volcanii follows protein translocation.
Once the newly synthesized surface (S)-layer glycoprotein of the halophilic archaeaon Haloferax volcanii has traversed the plasma membrane, the protein undergoes a membrane-related, Mg(2+)-dependent maturation event, revealed as an increase in the apparent molecular mass and hydrophobicity of the protein. To test whether lipid modification of the S-layer glycoprotein could explain these observations, H. volcanii cells were incubated with a radiolabelled precursor of isoprene, [(3)H]mevalonic acid. In Archaea, isoprenoids serve as the major hydrophobic component of archaeal membrane lipids and have been shown to modify other haloarchaeal S-layer glycoproteins, although little is known of the mechanism, site or purpose of such modification. In the present study we report that the H. volcanii S-layer glycoprotein is modified by a derivative of mevalonic acid and that maturation of the protein was prevented upon treatment with mevinolin (lovastatin), an inhibitor of mevalonic acid biosynthesis. These findings suggest that lipid modification of S-layer glycoproteins is a general property of halophilic archaea and, like S-layer glycoprotein glycosylation, lipid-modification of the S-layer glycoproteins takes place on the external cell surface, i.e. following protein translocation across the membrane.
Konrad
Zvia
Z
Department of Life Sciences, Ben Gurion University of the Negev, Beersheva 84105, Israel.
Eichler
Jerry
J
D000143:Acids / Q000494:pharmacology; D001105:Archaea / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D006023:Glycoproteins / Q000737:chemistry / Q000378:metabolism; D019621:Haloferax / Q000378:metabolism*; D050356:Lipid Metabolism; D008274:Magnesium / Q000378:metabolism; D008798:Mevalonic Acid / Q000378:metabolism*; D010455:Peptides / Q000737:chemistry; D017368:Protein Prenylation; D011499:Protein Processing, Post-Translational; D021381:Protein Transport; D013997:Time Factors
D000143:Acids; D006023:Glycoproteins; D010455:Peptides; D008274:Magnesium; D008798:Mevalonic Acid