Sequence of extracellular mouse protein BM-90/fibulin and its calcium-dependent binding to other basement-membrane ligands

Eur J Biochem. 1993 Aug 1;215(3):733-40. doi: 10.1111/j.1432-1033.1993.tb18086.x.


Partial sequence comparisons have recently indicated that two extracellular components, fibulin from human placenta and BM-90 from a basement-membrane-producing mouse tumor, are either identical or closely related proteins. In this study, a complete sequence analysis of mouse BM-90 cDNA showed a 539-residue N-terminal core structure (domains I and II), which was 85% identical with the same core structure of human fibulin. A 137-residue C-terminal sequence (domain III) was unique for BM-90 and could also be identified by Edman degradation. This suggested a novel splice product, variant D, which is characteristic for the mouse tumor. A second 117-residue C-terminal sequence (domain III) was identified in additional mouse cDNA clones and showed 91% identity with the region specific for variant C of fibulin. Northern blots using mouse cells demonstrated two mRNA species, 2.7 kb and 2.3 kb, which encoded the variants D and C, respectively. The sequence of BM-90/fibulin indicates the presence of nine epidermal-growth-factor-like repeats in the core domain-II structure, eight of which contain consensus motifs for calcium binding. This binding is apparently important for the interaction of BM-90 with laminin and nidogen and for some weaker interactions with collagen IV. Further binding of BM-90 was demonstrated to fibronectin and BM-90 itself, but did not depend on calcium. Major binding sites for BM-90 were identified at a C-terminal segment of laminin A chain and at the N-terminus of nidogen. The broad interaction repertoire of BM-90 is comparable to that of nidogen and both proteins may have similar roles as connecting elements in the extracellular matrix.

Publication types

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

MeSH terms

  • Alternative Splicing
  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Basement Membrane / metabolism
  • Calcium / metabolism*
  • Calcium-Binding Proteins / chemistry*
  • Calcium-Binding Proteins / genetics*
  • Calcium-Binding Proteins / metabolism
  • Cells, Cultured
  • Humans
  • Laminin / metabolism
  • Ligands
  • Membrane Glycoproteins / metabolism
  • Mice
  • Molecular Sequence Data
  • Protein Binding
  • RNA, Messenger / metabolism
  • Sequence Homology, Amino Acid
  • Tumor Cells, Cultured


  • Calcium-Binding Proteins
  • Laminin
  • Ligands
  • Membrane Glycoproteins
  • RNA, Messenger
  • fibulin
  • nidogen
  • Calcium

Associated data

  • GENBANK/L09682
  • GENBANK/L09683
  • GENBANK/L20347
  • GENBANK/L20348
  • GENBANK/X63070
  • GENBANK/X70853
  • GENBANK/X70854
  • GENBANK/X71339
  • GENBANK/X71340
  • GENBANK/X72968