IDENTIFICATION BY MOLECULAR-CLONING OF 2 CDNA SEQUENCES FROM THE PLANT BRASSICA-NAPUS WHICH ARE VERY SIMILAR TO MAMMALIAN PROTEIN PHOSPHATASES-1 AND PHOSPHATASES-2A

Two clones encoding protein phosphatase (PP) catalytic subunits have been isolated from a Brassica napus cDNA library screened with rabbit muscle PP1-alpha and PP2A-alpha cDNAs. The deduced protein sequences are very similar to those of mammalian PP1-alpha and PP2A-alpha (72% and 79% overall identity, respectively) indicating that they are the plant homologues of PP1-alpha and PP2A-alpha. This high degree of similarity provides a molecular explanation for the remarkable conservation of the catalytic and regulatory properties between animal and plant protein phosphatases and supports the concept that PP1 and PP2A may be the most highly conserved of known enzymes.