A fragmin-like protein from plasmodium of Physarum polycephalum that severs F-actin and caps the barbed end of F-actin in a Ca2+-sensitive way.
Many protein factors regulating actin polymerization can be extracted from plasmodia of Physarum polycephalum in the presence of a high EGTA concentration (30 mM). A protein factor with the molecular weight of 60,000 (60 kDa protein) was especially interesting because of its fragmin-like properties. We purified and characterized this 60 kDa protein in the present study. The purified 60 kDa protein enhanced the initial rate of G-actin polymerization, severed F-actin, and capped the barbed end of F-actin in a Ca2+-dependent way. The threshold concentration for Ca2+ was around 10(-6) M. The flow birefringence measurement showed that the length of F-actin decreased from 2.8 to 1.0 microns depending on the concentration of 60 kDa protein added to F-actin. These properties were identical to those of fragmin (Mr 42,000) isolated from plasmodia (Hasegawa et al. (1980) Biochemistry 19, 2677-2683). However, the molecular weight, the tryptic peptide map, and the cross-reactivities with polyclonal anti-fragmin antibodies were different from those of fragmin. We concluded from these results that 60 kDa protein is a new Ca2+-sensitive F-actin-severing protein. Considering its similarity to fragmin, we termed the 60 kDa protein fragmin 60.
Furuhashi
K
K
Department of Molecular Biology, Faculty of Science, Nagoya University, Aichi.
Hatano
S
S
D000199:Actins / Q000096:biosynthesis / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002848:Chromatography, DEAE-Cellulose; D003429:Cross Reactions; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D005656:Fungal Proteins / Q000032:analysis* / Q000276:immunology / Q000378:metabolism; D006495:Heparin, Low-Molecular-Weight / Q000032:analysis* / Q000378:metabolism; D010446:Peptide Fragments / Q000032:analysis / Q000276:immunology; D010804:Physarum / Q000378:metabolism*; D011189:Potassium Chloride; D011817:Rabbits; D013053:Spectrophotometry; D014357:Trypsin; D014783:Viscosity
D000199:Actins; D005656:Fungal Proteins; D006495:Heparin, Low-Molecular-Weight; D010446:Peptide Fragments; D011189:Potassium Chloride; D014357:Trypsin; D002118:Calcium