title: HIV-1 rsgp41 depends on calcium for binding of human c1q but not for binding of gp120.
abstract: Human immunodeficiency virus type 1 activates the complement cascade via the classical pathway by direct binding of C1q through specific sites in the TM surface protein, gp41. In this paper we investigated the divalent cation dependence of the interaction between HIV-1 gp41 and C1q or gp120. A solid phase radioimmunoassay was used to investigate the interaction between a recombinant soluble form of HIV-1 gp41 (rsgp41) and C1q and an enzyme linked immunoassay was used to investigate the interaction between rsgp41 and gp120. The interaction between C1q and rsgp41, but not between C1q and immune complexes, was dependent upon the presence of calcium. Calcium could not be replaced by larger cations such as strontium, barium, lead or smaller ions such as magnesium and manganese. Zinc increased binding to 22% of binding achieved with calcium. The interaction between rsgp41 and gp120 was not dependent upon the presence of divalent ions. Thus, calcium is required for the interaction between rsgp41 and C1q, whereas the interaction between rsgp41 and gp120 is independent of divalent cations.
authors.affiliation: Institut für Hygiene, Innsbruck, Austria.
authors.forename: H
authors.initials: H
authors.lastname: Stoiber
authors.forename: C F
authors.initials: CF
authors.lastname: Ebenbichler
authors.forename: N M
authors.initials: NM
authors.lastname: Thielens
authors.forename: G J
authors.initials: GJ
authors.lastname: Arlaud
authors.forename: M P
authors.initials: MP
authors.lastname: Dierich
mesh_terms: D002118:Calcium / Q000502:physiology*; D002413:Cations, Divalent; D015922:Complement C1q / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D015699:HIV Envelope Protein gp120 / Q000378:metabolism*; D015700:HIV Envelope Protein gp41 / Q000378:metabolism*; D015497:HIV-1 / Q000378:metabolism*; D006801:Humans; D011485:Protein Binding / Q000502:physiology; D011863:Radioimmunoassay; D011994:Recombinant Proteins / Q000378:metabolism
chemical_list: D002413:Cations, Divalent; D015699:HIV Envelope Protein gp120; D015700:HIV Envelope Protein gp41; D011994:Recombinant Proteins; D015922:Complement C1q; D002118:Calcium