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Characterization of the protein kinase activity in beet root plasma membranes
Author(s) -
BaizabalAguirre VíActor M.,
González de la Vara Luis E.
Publication year - 1994
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1994.tb00412.x
Subject(s) - autophosphorylation , biochemistry , gtp' , kinase , phosphorylation , phosphoprotein , chemistry , protein kinase a , casein kinase 1 , casein , membrane , casein kinase 2 , microbiology and biotechnology , biology , enzyme , mitogen activated protein kinase kinase
Two protein kinase activities were found in plasma membrane‐enriched preparations from red beet ( Beta vulgarix L.). The kinases in these preparations produced the phosphorylation of several membrane polypeptides. These kinases also phosphorylated histone III‐S and casein. The activities of two different kinases could be distinguished: one was half‐maximally stimulated by 1 μ M free Ca 2+ phosphorylated histone III‐S better than casein, showed half‐maximal activity at an ATP concentration of 0.071 m M . had an optimum pH of 7, and was poorly inhibited by GTP, CTP or UTP. Another, much lower, kinase activity that phosphorylated casein was also observed; it was Ca 2+ independent, showed half‐maximal activity at ATP concentrations of 0.017 and 0.287 m M , exhibited a broad pH optimum about pH 7 and was inhibited by GTP, CTP, UTP or GDP to a greater extent than the calcium‐stimulated activity. When plasma membrane proteins were solubilized with lysophosphatidyicholine and treated with [γ‐ 32 P]ATP at several dilutions, a 125‐kDa polypeptide was autophosphorylated in the absence of Ca 2+ , while 77‐, 71‐ and 65‐kDa polypeptides were autophosphorylated in its presence. Autophosphorylation in gels after electrophoresis showed a Ca 2+ ‐stimulated phosphoprotein band at 64 kDa.