Immunological characterization of phosphoprotein phosphatases.
Phosphoprotein phosphatases regulate the biological activities of proteins through their involvement in cyclic phosphorylation/dephosphorylation cascades. A variety of multimeric phosphatases have been isolated and grouped into several classes, termed type 1 and types 2A, 2B, and 2C. To elucidate the relationship between the different phosphoprotein phosphatases, highly purified enzymes from soil amoebae, turkey gizzards, bovine heart and brain, and rabbit skeletal muscle and reticulocytes were tested for immunological antigenic relatedness. Two heterologous antibody preparations were employed for this purpose. One was made against an Acanthamoeba type 2A phosphatase and the other was made to bovine brain phosphatase type 2B (calcineurin, holoenzyme). Specific subunit cross-reactivity was examined by protein blot ("Western") analysis. The antibody to the type 2A phosphatase reacted with the catalytic subunits of every type 2 enzyme tested, including both the catalytic and Ca2+-binding subunits of the Ca2+/calmodulin-dependent type 2B phosphatase (calcineurin), bovine cardiac type 2A phosphatase, and turkey gizzard smooth muscle phosphatase-1 (type 2A1). It did not react with any type 1 phosphatase (catalytic subunit or ATP-Mg-dependent). The antigenic relatedness of calcineurin and the bovine cardiac type 2A phosphatase (Mr 38,000) was demonstrated further by protein blot analysis showing that the anti-calcineurin antibody cross-reacted with both enzymes. The mutual cross-reactivity poses an intriguing problem because these enzymes are so different in their molecular structures and modes of regulation. The degree of evolutionary conservation exhibited by the antigenic cross-reactivity of the type 2 enzymes from a broad range of species and tissues suggests a strong selective pressure on maintaining one or more features of these important regulatory enzymes.
E
E
Shacter
J A
JA
McClure
E D
ED
Korn
P B
PB
Chock
D000818:Animals; D000906:Antibodies; D000936:Antigen-Antibody Complex; D001921:Brain / Q000201:enzymology; D002417:Cattle; D003429:Cross Reactions; D000939:Epitopes / Q000032:analysis*; D005895:Gizzard, Avian / Q000201:enzymology; D008970:Molecular Weight; D009132:Muscles / Q000201:enzymology; D009206:Myocardium / Q000201:enzymology; D010749:Phosphoprotein Phosphatases / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism*; D054645:Protein Phosphatase 1; D011817:Rabbits; D012156:Reticulocytes / Q000201:enzymology; D014422:Turkeys
D000906:Antibodies; D000936:Antigen-Antibody Complex; D000939:Epitopes; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1