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Direct metal analyses of Mn 2+ ‐dependent and ‐independent protein phosphatase 2A from human erythrocytes detect zinc and iron only in the Mn 2+ ‐independent one
Author(s) -
Nishito Yasumasa,
Usui Hirofumi,
Shinzawa-Itoh Kyoko,
Inoue Rintaro,
Tanabe Osamu,
Nagase Terumasa,
Murakami Takehiko,
Takeda Masao
Publication year - 1999
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(99)00256-2
Subject(s) - zinc , phosphatase , chemistry , manganese , protein subunit , cytosol , enzyme , papain , metal , biochemistry , nuclear chemistry , organic chemistry , gene
A Mn 2+ ‐dependent protein phosphatase 2A which is composed of a 34 kDa catalytic C′ subunit and a 63 kDa regulatory A′ subunit, was purified from human erythrocyte cytosol. C′ and A′ produced V8‐ and papain‐peptide maps identical to those of the 34 kDa catalytic C and the 63 kDa regulatory A subunits of the Mn 2+ ‐independent conventional protein phosphatase in human erythrocyte cytosol, respectively. Reconstitution of C′A and CA′ revealed that the metal dependency resided in C′ and not in A′. In CA, 0.87±0.12 mol zinc and 0.35±0.18 mol iron per mol enzyme were detected by atomic absorption spectrophotometry, but manganese, magnesium and cobalt were not detected. None of these metals was detected in C′A′. Pre‐incubation of C′ with ZnCl 2 and FeCl 2 , but not FeCl 3 , synergistically stimulated the Mn 2+ ‐independent protein phosphatase activity. The protein phosphatase activity of C was unaffected by the same zinc and/or iron treatment. These results suggest that C is a Zn 2+ ‐ and Fe 2+ ‐metalloenzyme and that C′ is the apoenzyme.