Calcyphosine (CAPS)

Calcyphosin is a calcium-binding protein with 4 EF-hand domains whose synthesis and phosphorylation is upregulated by cAMP agonists in thyrocytes. A similar protein was first described as a potentially important regulatory protein in the dog thyroid and was termed as R2D5 antigen in rabbit. Alternative splicing of this gene generates two transcript variants.Calcyphosine was first described as a potentially important regulatory protein in the dog thyroid.

The deduced 189-amino acid protein has a molecular mass of about 24 kD by Western blot analysis. Human CAPS shares extensive sequence conservation with the sequences from dog and rabbit. Northern and Western blot analyses revealed that expression in human thyroid tissue is relatively lower than that in dog.