title: Self-association of CPV3, an avian thymic parvalbumin.
abstract: The avian parvalbumin called CPV3 readily forms disulfide-linked oligomers. Sedimentation data presented herein reveal that CPV3 also undergoes noncovalent self-association. Interestingly, the noncovalent interaction is promoted by either Ca2+ or Mg2+, whereas covalent complex formation displays an absolute requirement for the Ca(2+)-bound protein. Apo-CPV3 exhibits an apparent sedimentation coefficient of 2.08 S at 20 degrees C, in 0.15 M NaCl, 0.025 M HEPES-NaOH, pH 7.4. This value increases to 2.85 S or 3.16 S with addition of 1.0 mM Ca2+ or 5.0 mM Mg2+, respectively. Least-squares analysis of sedimentation equilibrium data suggests that 100 microM apo-CPV3 is primarily a mixture of monomeric and dimeric forms. With the addition of Ca2+, the equilibrium becomes exclusively monomer-trimer, with negligible amounts of dimer. A comparable distribution is observed in the presence of Mg2+.
mesh_terms: D000818:Animals; D001059:Apoproteins / Q000737:chemistry; D001717:Birds; D002118:Calcium; D046911:Macromolecular Substances; D008274:Magnesium; D008433:Mathematics; D008958:Models, Molecular; D010320:Parvalbumins / Q000737:chemistry; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification; D013950:Thymus Gland / Q000378:metabolism*; D014461:Ultracentrifugation
chemical_list: D001059:Apoproteins; D046911:Macromolecular Substances; D010320:Parvalbumins; D011994:Recombinant Proteins; D008274:Magnesium; D002118:Calcium