Poly(L-proline)-binding proteins from chick embryos are a profilin and a profilactin

Eur J Biochem. 1985 Sep 2;151(2):291-7. doi: 10.1111/j.1432-1033.1985.tb09099.x.


Two poly(L-proline)-binding proteins (PBP-1 and PBP-2) were purified from chick embryos by using a poly(L-proline)-agarose column. PBP-1 was composed of two different polypeptides (molecular masses of 42 kDa and 15 kDa). The molar ratio of the two proteins in the complex was 1:1. The other poly(L-proline)-binding protein, PBP-2, was the 15-kDa protein itself. The 42-kDa protein was confirmed to be an actin from the amino acid composition, by immunochemical evidence and by its ability to self-polymerize. In addition, the 42 + 15-kDa protein complex (PBP-1) inhibited DNase I, just as a monomeric actin did. The amino acid composition of the 15-kDa protein was similar to that of mammalian profilin and it inhibited the salt-induced polymerization of rabbit skeletal muscle actin. Therefore, we conclude that the two poly(L-proline)-binding proteins from the chick embryo are a profilactin and a profilin in chick embryo. The ability of profilactin to bind poly(L-proline) must be due to profilin itself, because the profilin has a greater affinity for poly(L-proline) than does profilactin. Additionally, both the monomeric and filamentous actin from rabbit skeletal muscle have no affinity for poly(L-proline).

MeSH terms

  • Actins / metabolism
  • Amino Acid Transport Systems, Neutral*
  • Animals
  • Carrier Proteins / isolation & purification*
  • Chick Embryo
  • Chromatography, Affinity
  • Contractile Proteins*
  • Electrophoresis, Polyacrylamide Gel
  • Immunodiffusion
  • Microfilament Proteins*
  • Molecular Weight
  • Peptides / metabolism*
  • Profilins
  • Protein Conformation
  • Proteins / isolation & purification*


  • Actins
  • Amino Acid Transport Systems, Neutral
  • Carrier Proteins
  • Contractile Proteins
  • Microfilament Proteins
  • Peptides
  • Profilins
  • Proteins
  • profilactin
  • proline transport protein
  • polyproline