Purification and characterization of bovine profilin II. Actin, poly(L-proline) and inositolphospholipid binding.
We purified profilin from bovine brain and were able to separate the two isoforms present in this tissue. Since functional characteristics for profilin II are lacking, we assayed the actin, the phosphatidylinositol 4,5-bisphosphate and the poly(L-proline) binding properties of this isoform. Profilin II binds actin with a similar affinity to that of profilin I, although it inhibits actin polymerization more strongly than profilin I under non-equilibrium conditions. Profilin II also binds the anionic phospholipid phosphatidylinositol 4,5-bisphosphate. Profilin II binds to poly(L-proline) more strongly than does profilin I; this is especially evident at more acidic pH values. This difference is explained by an amino acid exchange in the carboxy-terminal part of the protein which has been implicated in poly(L-proline) binding [Björkegren, C., Rozycki, M., Schutt, C., Lindberg, U. & Karlsson, R. (1993) FEBS Lett. 333, 123-126; Metzler, W., Bell, A., Ernst, E., Lavoie, T. & Mueller, L. (1994) J. Biol. Chem. 369, 4620-4625].
Lambrechts
A
A
Flanders Institute of Biotechnology, University Ghent, Belgium.
van Damme
J
J
Goethals
M
M
Vandekerckhove
J
J
Ampe
C
C
D000199:Actins / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D003285:Contractile Proteins; D008840:Microfilament Proteins / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D008969:Molecular Sequence Data; D010455:Peptides / Q000378:metabolism; D019269:Phosphatidylinositol 4,5-Diphosphate; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism*; D051304:Profilins
D000199:Actins; D003285:Contractile Proteins; D008840:Microfilament Proteins; D010455:Peptides; D019269:Phosphatidylinositol 4,5-Diphosphate; D018129:Phosphatidylinositol Phosphates; D051304:Profilins; C011083:polyproline