title: Multimer formation by FKBP-12: roles for cysteine 23 and phenylalanine 36.
abstract: FKBP-12 mediates the immunosuppressive actions of FK506 and rapamycin, and modulates the activities of the ryanodine, IP3 and type 1 TGF-ss receptors. Additionally, FKBP-12 possesses cis-trans peptidylprolyl isomerase (rotamase) activity. We have discovered that recombinant FKBP-12 readily forms a dimer and a small amount of trimer under nonreducing conditions. A mutant with substitution at the sole cysteine residue of FKBP-12 (C23S) did not form dimers or trimers. Using mutants with 5% or less rotamase activity, the formation of dimers was independent of enzymatic activity. The formation of trimers was abrogated by a F36Y substitution, even though dimer formation was preserved. Dimers were also observed with native FKBP-12 that was detached from rabbit skeletal muscle ryanodine receptors using FK590. The multimers of FKBP-12 could interact with molecular targets distinctly from the FKBP-12 monomer, for example, by facilitating the assembly of multimeric receptors or coordinating the activity of receptor subunits.
authors.affiliation: Section of Cardiology, Department of Internal Medicine and Wake Forest University School of Medicine, Winston-Salem, NC 27157-1045, USA.
authors.forename: Barbara
authors.initials: B
authors.lastname: Schories
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Nelson
authors.forename: David C
authors.initials: DC
authors.lastname: Sane
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D003545:Cysteine / Q000235:genetics* / Q000502:physiology; D019281:Dimerization; D004591:Electrophoresis, Polyacrylamide Gel; D015151:Immunoblotting; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism; D009154:Mutation; D010649:Phenylalanine / Q000235:genetics* / Q000502:physiology; D011817:Rabbits; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D020539:Sequence Analysis, Protein; D022061:Tacrolimus Binding Protein 1A / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism
chemical_list: D050505:Mutant Proteins; D011994:Recombinant Proteins; D010649:Phenylalanine; D022061:Tacrolimus Binding Protein 1A; D003545:Cysteine