The mouse FKBP23 binds to BiP in ER and the binding of C‐terminal domain is interrelated with Ca2+ concentration

摘要

>FK506 binding protein 23 from mouse (mFKBP23) is a peptidyl-prolyl cis-trans isomerase (PPIase) from the endoplasmic reticulum (ER), which consists of an N-terminal PPIase domain and a C-terminal domain with Ca2+ binding sites. The assay of adsorption from ER extract with glutathione S-transferase-mFKBP23 attached to glutathione-Sepharose 4B shows that mFKBP23 binds to mouse immunoglobulin binding protein (mBiP). The same assay with the recombinant proteins of the N- and C-termini of mFKBP23 shows that the binding of the C-terminus is Ca2+-dependent and the switch point is between 2 and 3 mM. By high concentration of Ca2+ this binding cannot be detected. Furthermore, the Ca2+-regulated binding of mFKBP23 and mBiP in ER can be detected by means of co-immunoprecipitation.