Low nidogen affinity of laminin-5 can be attributed to two serine residues in EGF-like motif gamma 2III4.
High affinity nidogen binding of laminin-1 (chain composition alpha 1 beta 1 gamma 1) has been previously mapped to a single EGF-like motif gamma 1III4 of its gamma 1 chain. Two more isoforms, laminin-5 (alpha 3 beta 3 gamma 2) and laminin-7 (alpha 3 beta 2 gamma 1), show low and high binding activity, respectively, indicating that the gamma 2 chain is of low affinity. This was confirmed by recombinant production of the homologous EGF-like motif gamma 2III4 of the gamma 2 chain, which has a 100,000-fold lower binding activity than gamma 1III4. The crucial heptapeptide binding sequence Asn-Ile-Asp-Pro-Asn-Ala-Val of gamma 1III4 is modified in gamma 2III4 by replacing both the central Asn and Val by Ser. Changing these replacements to Asn and Val by site-directed mutagenesis enhanced the activity of gamma 2III4 to a level which was only 5-fold lower than that of gamma 1III4. Despite their high sequence identity (77%) motifs gamma 1III4 and gamma 2III4 were also shown to differ considerably in immunological epitopes. This indicates distinctly different functions for laminins which differ in the gamma chain isoform.
Mayer
U
U
Max-Planck-Institut für Biochemie, Martinsried, Germany.
Pöschl
E
E
Gerecke
D R
DR
Wagman
D W
DW
Burgeson
R E
RE
Timpl
R
R
D000595:Amino Acid Sequence; D001216:Asparagine; D001483:Base Sequence; D001485:Basement Membrane / Q000378:metabolism; D001665:Binding Sites; D015815:Cell Adhesion Molecules / Q000737:chemistry* / Q000378:metabolism*; D002460:Cell Line; D017931:DNA Primers; D004815:Epidermal Growth Factor / Q000737:chemistry*; D006801:Humans; D007700:Kinetics; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000378:metabolism*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D017354:Point Mutation; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012694:Serine; D014162:Transfection; D014633:Valine; D000097794:Kalinin
D001216:Asparagine; D015815:Cell Adhesion Molecules; D017931:DNA Primers; D004815:Epidermal Growth Factor; D008562:Membrane Glycoproteins; D011994:Recombinant Proteins; D012694:Serine; D014633:Valine; D000097794:Kalinin; C029967:nidogen