Cloning and characterization of a transmembrane serine kinase that acts as an activin type I receptor

Proc Natl Acad Sci U S A. 1993 Dec 1;90(23):11242-6. doi: 10.1073/pnas.90.23.11242.


Activin type II receptors are transmembrane protein-serine/threonine kinases. By using a reverse-transcription PCR assay to screen for protein kinase sequences, we isolated a cDNA clone, activin X1 receptor, from rat brain that encodes a 55-kDa transmembrane protein-serine kinase which is structurally related to other receptors in this kinase subfamily. The predicted protein consists of 509 amino acids, and the kinase domain shows 40% and 37% identity to the activin and transforming growth factor beta type II receptors, respectively. No activin-binding was observed when activin X1 receptor was expressed alone in COS-M6 cells; however, coexpression with type II activin receptors gave rise to a 68-kDa affinity-labeled complex in addition to the 85-kDa type II receptor complex. The size of this cross-linked band is consistent with the size of the type I activin receptor; furthermore, activin X1 receptor associated with type II receptors, as judged by coimmunoprecipitation with type II receptor antibodies. These data suggest that activin X1 receptor can serve as an activin type I receptor and that the diverse biological effects of activins may be mediated by a complex formed by the interaction of two transmembrane protein-serine kinases.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Activin Receptors
  • Animals
  • Base Sequence
  • Cloning, Molecular
  • DNA Primers / chemistry
  • DNA, Complementary / genetics
  • Gene Expression
  • Molecular Sequence Data
  • Precipitin Tests
  • Protein Serine-Threonine Kinases / genetics*
  • RNA, Messenger / genetics
  • Rats
  • Receptors, Cell Surface / genetics*
  • Receptors, Growth Factor / genetics*
  • Receptors, Transforming Growth Factor beta / chemistry
  • Tissue Distribution
  • Transfection


  • DNA Primers
  • DNA, Complementary
  • RNA, Messenger
  • Receptors, Cell Surface
  • Receptors, Growth Factor
  • Receptors, Transforming Growth Factor beta
  • Protein Serine-Threonine Kinases
  • Activin Receptors

Associated data

  • GENBANK/L19341