Open AccessAn 100‐kDa Ca 2+ ‐sensitive actin‐fragmenting protein from unfertilized sea urchin egg
Author(s) -
HOSOYA Hiroshi,
MABUCHI Issei,
SAKAI Hikoichi
Publication year - 1986
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1986.tb09387.x
Subject(s) - actin , stokes radius , size exclusion chromatography , molecular mass , sodium dodecyl sulfate , gel electrophoresis , polymerization , chemistry , actin binding protein , protein filament , biophysics , biochemistry , biology , cytoskeleton , actin cytoskeleton , polymer , organic chemistry , cell , enzyme
An actin‐modulating protein was purified from unfertilized eggs of sea urchin, Hemicentrotus pulcherrimus , by means of DNase I affinity and DEAE‐cellulose column chromatographies. This protein was a globular protein with a Stokes radius of 41‐42 nm and consisted of a single polypeptide chain having an apparent molecular mass of 100 kDa on sodium dodecyl sulfate polyacrylamide gel electrophoresis. Gel filtration chromatography revealed that one 100‐kDa protein molecule binds two or three actin monomers in the presence of Ca 2+ , but such binding was not observed in the absence of Ca 2+ . The effect of the 100‐kDa protein on the polymerization of actin was studied by viscometry, spectrophotometry and electron microscopy. The initial rate of actin polymerization was decreased at a very low molar ratio of 100‐kDa protein/actin. Acceleration of the initial rate of polymerization occurred at a relatively high, but still substoichiometric, molar ratio of 100‐kDa protein actin. The 100‐kDa protein produced fragmentation of muscle actin filaments at Ca 2+ ‐ concentrations greater than 0.3 μM as revealed by viscometry and electron microscopy. Evidence was also presented that the 100‐kDa protein binds to the barbed end of the actin filament.