The alternatively spliced type III connecting segment of fibronectin is a zinc-binding module.
Fibronectin (FN) is a prototypic adhesive glycoprotein that is widely expressed in extracellular matrices and body fluids. The fibronectin molecule is dimeric, and composed of a series of repeating polypeptide modules. A recombinant fragment of FN incorporating type III repeats 12-15, and including the alternatively-spliced type three connecting segment (IIICS), was found to bind Ni(2+), Cu(2+) and Zn(2+) divalent cations, whereas a similar fragment lacking the IIICS did not. Mutation of two pairs of histidine residues in separate spliced regions of the IIICS reduced cation binding to near the level of the variant lacking the IIICS, suggesting a zinc finger-like mode of cation coordination. Analysis of native FNs purified from plasma or amniotic fluid revealed significant levels of zinc associated with those isoforms that contain the complete IIICS. Taken together, these data demonstrate that the IIICS region of FN is a novel zinc-binding module.
Askari
Janet A
JA
Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom.
Thornton
David J
DJ
Humphries
Jonathan D
JD
Buckley
Patrick A
PA
Humphries
Martin J
MJ
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000653:Amniotic Fluid / Q000737:chemistry; D001665:Binding Sites; D001667:Binding, Competitive; D002413:Cations, Divalent / Q000378:metabolism; D002448:Cell Adhesion / Q000502:physiology; D003300:Copper / Q000378:metabolism; D005353:Fibronectins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006639:Histidine / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009532:Nickel / Q000378:metabolism; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D015032:Zinc / Q000032:analysis / Q000378:metabolism*
D002413:Cations, Divalent; D005353:Fibronectins; D010446:Peptide Fragments; D020033:Protein Isoforms; D011994:Recombinant Proteins; D006639:Histidine; D003300:Copper; D009532:Nickel; D015032:Zinc