p36, the major cytoplasmic substrate of src tyrosine protein kinase, binds to its p11 regulatory subunit via a short amino-terminal amphiphatic helix

EMBO J. 1988 Aug;7(8):2435-42. doi: 10.1002/j.1460-2075.1988.tb03089.x.

Abstract

Protein I is a hetero-tetramer which contains two copies each of p11 and p36. p36 (calpactin I, lipocortin II) is a major substrate of retrovirally encoded tyrosine protein kinases, while p11 modulates several Ca2+-induced properties also displayed by p36 alone. Here we have characterized the p11 binding site on p36 by fluorescence spectroscopy using porcine p36 labelled at cysteine 8 with the fluorophore Prodan (6-proprionyl-2-dimethylamino-naphthalene). We have used peptides of differing length from the amino-terminal domain of p36 to restrict the major binding site to the first 12 residues. Noticeable binding is still observed with a peptide containing only the first nine residues. Interestingly the N-terminal acetyl group of p36 forms a functional part of the p11 binding site. CD studies indicate that the binding region can form an alpha-helix, which seems to have amphiphatic properties when projected on a helical wheel. This structural element is also known for a calmodulin binding protein. Thus the question is raised whether other p11/calmodulin-related proteins interact with their target proteins via a similar mechanism. We also discuss how p11 could modulate p36 associated properties.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Annexins
  • Binding Sites
  • Calcium-Binding Proteins / analysis
  • Calcium-Binding Proteins / metabolism*
  • Chickens
  • Chromatography, Gel
  • Fluorescence Polarization
  • Glycoproteins / analysis
  • Glycoproteins / metabolism*
  • Molecular Sequence Data
  • Nerve Tissue Proteins / metabolism*
  • Peptides / chemical synthesis
  • Spectrometry, Fluorescence
  • Swine
  • Synapsins

Substances

  • Annexins
  • Calcium-Binding Proteins
  • Glycoproteins
  • Nerve Tissue Proteins
  • Peptides
  • Synapsins