FKBP12s

FKBP12s, also known as FK506-binding proteins of 12 kDa, are a family of immunophilins. These proteins are characterized by their ability to bind to the immunosuppressive drug FK506 (tacrolimus) and other macrolide compounds. They are ubiquitous in eukaryotes and play crucial roles in various cellular processes, including protein folding, signal transduction, and gene transcription.

The primary function of FKBP12s is as peptidyl-prolyl cis-trans isomerases. They catalyze the isomerization of peptide bonds preceding proline residues, a rate-limiting step in the folding of many proteins. This enzymatic activity helps in achieving the correct three-dimensional structure of proteins, essential for their proper function.

Beyond protein folding, FKBP12s act as molecular chaperones and scaffolds. They can interact with a diverse range of cellular proteins, including ion channels, growth factor receptors, and signaling molecules. By binding to these partners, FKBP12s can modulate their activity, localization, and stability. For instance, FKBP12s are known to regulate the function of calcium channels like the ryanodine receptor and the L-type calcium channel.

FKBP12s are also implicated in the regulation of gene expression. They can interact with transcription factors and coactivators, influencing the assembly of transcription complexes and thereby affecting the rate of gene transcription. Their involvement in these diverse cellular pathways highlights their importance in maintaining cellular homeostasis and responding to various stimuli.