An inactive protein phosphatase 2A population is associated with methylesterase and can be re-activated by the phosphotyrosyl phosphatase activator.
We have described recently the purification and cloning of PP2A (protein phosphatase 2A) leucine carboxylmethyltransferase. We studied the purification of a PP2A-specific methylesterase that co-purifies with PP2A and found that it is tightly associated with an inactive dimeric or trimeric form of PP2A. These inactive enzyme forms could be reactivated as Ser/Thr phosphatase by PTPA (phosphotyrosyl phosphatase activator of PP2A). PTPA was described previously by our group as a protein that stimulates the in vitro phosphotyrosyl phosphatase activity of PP2A; however, PP2A-specific methyltransferase could not bring about the activation. The PTPA activation could be distinguished from the Mn2+ stimulation observed with some inactive forms of PP2A, also found associated with PME-1 (phosphatase methylesterase 1). We discuss a potential new function for PME-1 as an enzyme that stabilizes an inactivated pool of PP2A.
Longin
Sari
S
Afdeling Biochemie, Faculteit Geneeskunde, Katholieke Universiteit Leuven, B-3000 Leuven, Belgium.
Jordens
Jan
J
Martens
Ellen
E
Stevens
Ilse
I
Janssens
Veerle
V
Rondelez
Evelien
E
De Baere
Ivo
I
Derua
Rita
R
Waelkens
Etienne
E
Goris
Jozef
J
Van Hoof
Christine
C
D000818:Animals; D001704:Biopolymers; D001921:Brain / Q000201:enzymology; D002265:Carboxylic Ester Hydrolases / Q000302:isolation & purification / Q000502:physiology*; D004789:Enzyme Activation; D008274:Magnesium / Q000494:pharmacology; D008345:Manganese / Q000494:pharmacology; D009124:Muscle Proteins / Q000302:isolation & purification / Q000502:physiology; D018482:Muscle, Skeletal / Q000201:enzymology; D009419:Nerve Tissue Proteins / Q000302:isolation & purification / Q000502:physiology; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D011497:Protein O-Methyltransferase / Q000235:genetics / Q000378:metabolism; D054648:Protein Phosphatase 2; D011506:Proteins / Q000235:genetics / Q000502:physiology; D011817:Rabbits; D011994:Recombinant Proteins / Q000378:metabolism; D013552:Swine
D001704:Biopolymers; D009124:Muscle Proteins; D009419:Nerve Tissue Proteins; D011506:Proteins; D011994:Recombinant Proteins; D008345:Manganese; C085457:C-terminal leucine protein methyltransferase; D011497:Protein O-Methyltransferase; D002265:Carboxylic Ester Hydrolases; C119357:protein phosphatase methylesterase-1; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2; D008274:Magnesium