title: Characterization of a human high density lipoprotein-associated protein, NA1/NA2. Identity with SP-40,40, an inhibitor of complement-mediated cytolysis.
abstract: Two peptides, NA1 and NA2, which we previously suggested to be associated with high density lipoproteins (HDLs), have been purified. Polyclonal antibodies against each peptide and a monoclonal antibody against NA2 have been used to further characterize them and their association with HDL. Immunoblotting studies revealed that the peptides form a complex of molecular mass of approximately 80 kd. Agarose gel filtration showed coelution of NA1/NA2 and apolipoprotein (apo) A-I, the structural protein of HDL. This was confirmed by fast protein liquid chromatography, which further indicated that up to 60% of NA1/NA2 was located within the lower density range of the HDL spectrum. Complementary studies with anti-apo A-I immunoaffinity columns provided evidence that at least 40% of NA1/NA2 was associated with HDL, an association easily disrupted by ultracentrifugal manipulation. Finally, partial amino acid sequences showed virtually complete homology with a recently identified protein, SP-40,40, or cytolysis inhibitor. The protein is suggested to have a powerful inhibitory effect on complement-mediated cell lysis. Our results could thus furnish an explanation for the previously observed modulating influence of HDL on complement activity.
authors.affiliation: Department of Medicine, University Hospital, Geneva, Switzerland.
authors.forename: R W
authors.initials: RW
authors.lastname: James
authors.forename: A C
authors.initials: AC
authors.lastname: Hochstrasser
authors.forename: I
authors.initials: I
authors.lastname: Borghini
authors.forename: B
authors.initials: B
authors.lastname: Martin
authors.forename: D
authors.initials: D
authors.lastname: Pometta
authors.forename: D
authors.initials: D
authors.lastname: Hochstrasser
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D016632:Apolipoprotein A-I; D001054:Apolipoproteins A / Q000276:immunology; D001798:Blood Proteins / Q000737:chemistry* / Q000302:isolation & purification; D002846:Chromatography, Affinity; D002850:Chromatography, Gel; D051152:Clusterin; D006023:Glycoproteins; D006801:Humans; D007118:Immunoassay; D015151:Immunoblotting; D008075:Lipoproteins, HDL / Q000032:analysis; D018832:Molecular Chaperones; D008969:Molecular Sequence Data; D008970:Molecular Weight; D012689:Sequence Homology, Nucleic Acid
chemical_list: D000596:Amino Acids; D016632:Apolipoprotein A-I; D001054:Apolipoproteins A; D001798:Blood Proteins; C495242:CLU protein, human; D051152:Clusterin; D006023:Glycoproteins; D008075:Lipoproteins, HDL; D018832:Molecular Chaperones