title: Distinct biochemical characteristics of the two human profilin isoforms.
abstract: The biochemical characteristics of a new human profilin isoform are described. We refer to this recently described isoform as profilin II (isoelectric point 5.9) in comparison to profilin I (pI 8.4). We expressed both isoforms in bacteria and compared their actin-binding properties, binding to poly(L-proline), affinities for phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2], and their effects on nucleotide exchange on actin. Profilin I and profilin II have similar affinities for PtdIns(4,5)P2 and poly(L-proline), and both accelerate nucleotide exchange on monomeric actin to the same extent. However, the affinity of profilin I for monomeric actin is about five times higher than the affinity of profilin II for actin. Potential structural differences of profilin I and profilin II that might explain the difference in actin binding are discussed.
authors.affiliation: Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: R
authors.initials: R
authors.lastname: Gieselmann
authors.forename: D J
authors.initials: DJ
authors.lastname: Kwiatkowski
authors.forename: P A
authors.initials: PA
authors.lastname: Janmey
authors.forename: W
authors.initials: W
authors.lastname: Witke
mesh_terms: D000199:Actins / Q000378:metabolism; D000595:Amino Acid Sequence; D003285:Contractile Proteins; D004926:Escherichia coli / Q000235:genetics; D015870:Gene Expression; D006801:Humans; D007526:Isoelectric Point; D008840:Microfilament Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D008969:Molecular Sequence Data; D009711:Nucleotides / Q000378:metabolism; D010455:Peptides / Q000378:metabolism; D019269:Phosphatidylinositol 4,5-Diphosphate; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D051304:Profilins; D017433:Protein Structure, Secondary
chemical_list: D000199:Actins; D003285:Contractile Proteins; D008840:Microfilament Proteins; D009711:Nucleotides; C495738:PFN1 protein, human; C495741:PFN2 protein, human; D010455:Peptides; D019269:Phosphatidylinositol 4,5-Diphosphate; D018129:Phosphatidylinositol Phosphates; D051304:Profilins; C011083:polyproline