Characterization of a novel calcium-binding 90-kDa glycoprotein (BM-90) shared by basement membranes and serum.
The protein BM-90 was solubilized from the mouse Engelbreth-Holm-Swarm tumor with neutral buffers in molar yields lower (15-30%) than found for other basement membrane proteins (e.g. laminin, BM-40). The purified protein was shown to be rich in cysteine (5 mol%) and to change in SDS electrophoresis from an 84-kDa position to a 95-kDa one upon reduction. BM-90 was also shown to be a calcium-binding protein. The N-terminal sequence of BM-90, as well as those of several internal peptides, showed no identity with any known protein sequences, indicating that it is a new protein. Specific radioimmunoassays showed no or only minor cross-reactions with other known basement membrane proteins. Immunological assays demonstrated BM-90 to be present in neutral salt extracts from mouse heart and kidney, in serum (20-40 micrograms/ml) and in the medium of various cultured cells (0.1-1 microgram/ml). The protein in these samples was identical in size to BM-90 purified from the tumor, indicating that negligible degradation occurs during purification. An extracellular matrix localization of BM-90 was shown by immunofluorescence for Reichert's membrane, lens capsules and other basement membranes. Thus, BM-90 appears to be a novel basement membrane protein whose functions remain to be studied.
Kluge
M
M
Max-Planck-Institut für Biochemie, Martinsried, Federal Republic of Germany.
Mann
K
K
Dziadek
M
M
Timpl
R
R
D000595:Amino Acid Sequence; D000818:Animals; D001485:Basement Membrane / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000097:blood / Q000302:isolation & purification / Q000378:metabolism*; D002848:Chromatography, DEAE-Cellulose; D002850:Chromatography, Gel; D004591:Electrophoresis, Polyacrylamide Gel; D010450:Endopeptidases; D005455:Fluorescent Antibody Technique; D007668:Kidney / Q000378:metabolism; D007700:Kinetics; D008562:Membrane Glycoproteins / Q000097:blood / Q000302:isolation & purification / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009206:Myocardium / Q000378:metabolism; D009374:Neoplasms, Experimental / Q000378:metabolism; D010446:Peptide Fragments / Q000302:isolation & purification
D002135:Calcium-Binding Proteins; D008562:Membrane Glycoproteins; D010446:Peptide Fragments; D010450:Endopeptidases; D002118:Calcium