title: A chimeric protein of simian immunodeficiency virus envelope glycoprotein gp140 and Escherichia coli aspartate transcarbamoylase.
abstract: The envelope glycoproteins of the human immunodeficiency virus and the related simian immunodeficiency virus (SIV) mediate viral entry into host cells by fusing viral and target cell membranes. We have reported expression, purification, and characterization of gp140 (also called gp160e), the soluble, trimeric ectodomain of the SIV envelope glycoprotein, gp160 (B. Chen et al., J. Biol. Chem. 275:34946-34953, 2000). We have now expressed and purified chimeric proteins of SIV gp140 and its variants with the catalytic subunit (C) of Escherichia coli aspartate transcarbamoylase (ATCase). The fusion proteins (SIV gp140-ATC) bind viral receptor CD4 and a number of monoclonal antibodies specific for SIV gp140. The chimeric molecule also has ATCase activity, which requires trimerization of the ATCase C chains. Thus, the fusion protein is trimeric. When ATCase regulatory subunit dimers (R(2)) are added, the fusion protein assembles into dimers of trimers as expected from the structure of C(6)R(6) ATCase. Negative-stain electron microscopy reveals spikey features of both SIV gp140 and SIV gp140-ATC. The production of the fusion proteins may enhance the possibilities for structure determination of the envelope glycoprotein either by electron cryomicroscopy or X-ray crystallography.
authors.affiliation: Laboratory of Molecular Medicine, The Children's Hospital, Boston, Massachusetts 02115, USA.
authors.forename: Bing
authors.initials: B
authors.lastname: Chen
authors.forename: Yifan
authors.initials: Y
authors.lastname: Cheng
authors.forename: Lesley
authors.initials: L
authors.lastname: Calder
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Harrison
authors.forename: Ellis L
authors.initials: EL
authors.lastname: Reinherz
authors.forename: John J
authors.initials: JJ
authors.lastname: Skehel
authors.forename: Don C
authors.initials: DC
authors.lastname: Wiley
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001221:Aspartate Carbamoyltransferase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016466:CHO Cells; D002478:Cells, Cultured; D006224:Cricetinae; D019281:Dimerization; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D015686:Gene Products, env / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D009036:Moths; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015302:Simian Immunodeficiency Virus / Q000235:genetics / Q000378:metabolism*
chemical_list: D015686:Gene Products, env; D011993:Recombinant Fusion Proteins; D001221:Aspartate Carbamoyltransferase