Biochemical characterization of profilin from seeds of Phaseolus vulgaris L.

The isoform composition of the 14.4kDa profilin polypeptide was analyzed in seeds, leaves, flowers, roots and root-nodules from Phaseolus vulgaris L. Isoforms of pIs similar to4.4-5 were present in all the tissues analyzed. T he bio-chemical features of the protein present in seed tissue were determi ned. Seed profilin bound to Phenyl-Sepharose under low salt conditions whic h suggested a hydrophobic interaction; however, it was not associated with micro-somal membranes nor it partitioned as a hydrophobic protein in Triton X-114. Fractions eluting from poly-L-proline or Phenyl-Sepharose columns c ontained well detectable amounts of profilin but no actin, suggesting that most of the protein was not present as profilactin in the seed. However, se ed profilin appeared to be in some kind of complex since several molecular weight species were observed on native gels. In addition, profilin was foun d preferentially in the embryo axis and light microscopic immunolocalizatio n showed a cytoplasmic distribution in this tissue.