title: Dissociation of peripheral protein-membrane complexes by high pressure.
abstract: The ability of high pressure to dissociate several peripheral protein-membrane complexes was investigated. Three vitamin K-dependent proteins (factor X, protein Z, and prothrombin) dissociated from small unilamellar vesicles (SUVs, 30 nm diameter) composed of 25% phosphatidylserine (PS) and 75% phosphatidylcholine (PC) at comparable pressures (midpoints of 0.3-0.6 kbar). The pressure-induced dissociation curves for the factor X-SUV interaction followed the expected behavior for an interaction with an apparent dissociation equilibrium constant at atmospheric pressure, KD(atm), of 9 x 10(-7) M and a change in volume of association, delta Va, of 88 mL/mol. Factor X also dissociated from large unilamellar vesicles (LUVs, 100 nm diameter, 25% PS:75% PC) with a midpoint of 0.5 kbar. A second group of calcium-dependent membrane-binding proteins included protein kinase C (PKC), a 64-kDa protein, and a 32-kDa protein. The 32-kDa protein dissociated from SUVs (midpoint of 0.8 kbar), whereas PKC and the 64-kDa protein did not dissociate to a significant degree. The differences in dissociability of these proteins appeared to be a result of the differences in their KD(atm)'s (decreased dissociability with decreased KD(atm)). This pattern was further demonstrated by the relatively high midpoint of dissociation (1.1-1.4 kbar) of serum amyloid P component (SAP; KD(atm) ca. 10(-11)) and the limited dissociation of factor Va light chain (KD(atm) ca. 10(-11)). Changing the vesicle composition to phosphatidylethanolamine in place of PC gave higher affinity and decreased dissociation of the 32-kDa protein and SAP.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Biochemistry, University of Minnesota, St. Paul 55108.
authors.forename: D A
authors.initials: DA
authors.lastname: Plager
authors.forename: G L
authors.initials: GL
authors.lastname: Nelsestuen
mesh_terms: D001798:Blood Proteins / Q000737:chemistry; D002135:Calcium-Binding Proteins / Q000737:chemistry; D004735:Energy Transfer; D005170:Factor X / Q000737:chemistry; D005453:Fluorescence; D006874:Hydrostatic Pressure; D008027:Light; D008081:Liposomes / Q000737:chemistry; D008565:Membrane Proteins / Q000737:chemistry*; D008956:Models, Chemical; D011516:Prothrombin / Q000737:chemistry; D012542:Scattering, Radiation
chemical_list: D001798:Blood Proteins; D002135:Calcium-Binding Proteins; D008081:Liposomes; D008565:Membrane Proteins; C026080:plasma protein Z; D011516:Prothrombin; D005170:Factor X