Biochemical analysis of mouse FKBP60, a novel member of the FKPB family

We have identified mouse and human FKBP60, a new member of the FKBP gene fa mily. FKBP60 shares strongest homology with FKBP65 and SMAP. FKBP60 contain s a hydrophobic signal peptide at the N-terminus, 4 peptidyl-prolyl cis/tra ns isomerase (PPIase) domains and an endoplasmic reticulum retention motif (HDEL) at the C-terminus. Immunodetection of HA-tagged FKBP60 in NIH-3T3 ce lls suggests that FKBP60 is segregated to the endoplasmic reticulum. Northe rn blot analysis shows that FKBP60 is predominantly expressed in heart, ske letal muscle, lung, liver and kidney. With N-succinyl-Ala-Ala-Pro-Phe-p-nit roanilide as a substrate, recombinant GST-FKBP60 is shown to accelerate eff ectively the isomerization of the peptidyl-prolyl bond. This isomerization activity is inhibited by FK506. mFKBP60 binds Ca2+ in vitro, presumably by its C-terminal EF-hand Ca2+ binding motif, and is phosphorylated in vivo, h FKBP60 has been mapped to 7p12 and/or 7p14 by fluorescence in situ hybridiz ation (FISH). (C) 1999 Elsevier Science B.V. All rights reserved.