Effect of NaF on type-1 phosphatase aggregation.

In muscle cytosolic and glycogen fractions prepared in the presence of 50 mM NaF phosphorylase phosphatase was a approximately 70 kDa complex instead of the 250 kDa or higher seen in the absence of NaF. A approximately 70 kDa complex was also formed when purified 37 kDa phosphatase-1 catalytic subunit (but not its 33 kDa tryptic fragment) was exposed to NaF. Treating this latter complex with a cross-linker led to disappearance of the 37 kDa protein and formation of a approximately 66 kDa band (detected by SDS electrophoresis), thus indicating the dimeric nature of the approximately 70 kDa complex.