Interaction of β2-glycoprotein 1 with phosphatidylserine-containing membranes: Ligand-dependent conformational alterations initiate bivalent binding

Randala Hamdan, Sourindra N. Maiti, Alan J. Schroit

Research output: Contribution to journalArticle

21 Scopus citations

Abstract

β2-Glycoprotein 1 (β2GP1), a 50 kDa serum glycoprotein that binds anionic phospholipid-containing membranes, plays a regulatory role in physiology and pathology. The protein is a member of the short consensus repeat (SCR) superfamily containing four typical repeating domains and an aberrant fifth domain constructed into an SCR-like core at the C-terminus. To investigate the contribution of the individual domains to the binding of β2GP1, a series of sequential domain-deleted recombinant protein fragments were generated and assessed for their interaction with PS-containing vesicles. Spectral analyses of lipid binding-dependent alterations in tryptophan emission spectra revealed that the (single) tryptophan residues of the individual domains underwent binding-dependent conformational alterations. Depending on the ionic strength, some domains moved from polar to nonpolar environments, while others moved from less polar to more polar environments. Analysis of a series of acrylamide quenching and resonance energy transfer experiments indicated that the binding of N-terminal domain 1 to PS membranes exists in two, ionic strength-dependent, conformations. At low ionic strengths, domain 1 bound to the vesicles and induced their precipitation and/or aggregation. At physiologic ionic strengths, domain 1 detached from the membrane surface while the remaining domains maintained their association with the membrane. Under these conditions, membrane-bound conformationally altered domain 1 projects away from the membrane surface, enabling it to interact with other proteins and/or cell surface ligands or receptors.

Original languageEnglish (US)
Pages (from-to)10612-10620
Number of pages9
JournalBiochemistry
Volume46
Issue number37
DOIs
StatePublished - Sep 18 2007

ASJC Scopus subject areas

  • Biochemistry

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