A novel human actin-binding protein homologue that binds to platelet glycoprotein Ibalpha

Blood. 1998 Aug 15;92(4):1268-76.


Glycoprotein (GP)Ib-IX-V is one of the major transmembrane complexes present on the platelet surface. Its extracellular domain binds von Willebrand factor (vWF) and thrombin, while its intracellular domain associates tightly with the cytoskeleton through the actin-binding protein (ABP)-280, also known as filamin. In the present study, a full-length cDNA coding for a human ABP homologue has been cloned and sequenced. This protein was identified by the yeast two-hybrid screening procedure via its interaction with the intracellular domain of GPIbalpha. Initially, a 1.3-kb partial cDNA was isolated from a megakaryocyte-like cell line (K562) cDNA library followed by a full-length cDNA of 9.4 kb that was identified in a human placenta library. The full-length cDNA encoded a protein of 2,578 amino acids with a calculated molecular weight of 276 kD (ABP-276). The amino terminal 248 amino acids contained an apparent actin binding domain followed by 24 tandem repeats each containing about 96 amino acids. The amino acid sequence of the protein shared a high degree of homology with human endothelial ABP-280 (70% identity) and chicken filamin (83% identity). However, the 32 amino acid Hinge I region in ABP-280 that contains a calpain cleavage site conferring flexibility on the molecule, was absent in the homologue. An isoform containing a 24 amino acid insertion with a unique sequence at the missing Hinge I region was also identified (ABP-278). This isoform resulted from alternative RNA splicing. ABP-276 and/or ABP-278 were present in all tissues examined, but the relative amount varied in that some tissue contained both forms, while other tissue contained predominately one or the other.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Base Sequence
  • Contractile Proteins / chemistry
  • Contractile Proteins / genetics
  • Contractile Proteins / isolation & purification*
  • Contractile Proteins / metabolism
  • DNA, Complementary / genetics
  • DNA, Neoplasm / genetics
  • Filamins
  • Humans
  • Leukemia, Erythroblastic, Acute / genetics
  • Microfilament Proteins / chemistry
  • Microfilament Proteins / genetics
  • Microfilament Proteins / isolation & purification*
  • Microfilament Proteins / metabolism
  • Molecular Sequence Data
  • Neoplasm Proteins / genetics
  • Neoplasm Proteins / isolation & purification
  • Neoplasm Proteins / metabolism
  • Organ Specificity
  • Platelet Glycoprotein GPIb-IX Complex / metabolism*
  • Protein Binding
  • RNA Splicing
  • Saccharomyces cerevisiae / genetics
  • Sequence Alignment
  • Sequence Homology, Amino Acid
  • Structure-Activity Relationship


  • Contractile Proteins
  • DNA, Complementary
  • DNA, Neoplasm
  • FLNB protein, human
  • Filamins
  • Microfilament Proteins
  • Neoplasm Proteins
  • Platelet Glycoprotein GPIb-IX Complex

Associated data

  • GENBANK/AF043045