The structure of the B subunit of calcineurin

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Abstract
The complete primary structure of the B subunit of calcineurin (protein phosphatase 2B) has been determined by automated sequence analysis. The protein consists of a single polypeptide chain of 168 residues, relative molecular mass 19200. The structure shows 35% identity with the sequence of calmodulin and 29% with troponin C. Homology is mainly confined to the regions of the four putative Ca2+‐binding loops. The results demonstrate that the B subunit is a new member of this family of Ca2+‐binding proteins. The N‐terminal glycine residue is blocked with the C14‐saturated fatty acid myristic acid and the first four residues are very similar to those of the catalytic subunit of cyclic‐AMP‐dependent protein kinase which also contains a myristoyl blocking group.