Elements in the C terminus of apolipoprotein [a] responsible for the binding to the tenth type III module of human fibronectin.
In previous studies, we showed that the C-terminal domain, F2, but not the N-terminal domain, F1, is responsible for the binding of apolipoprotein [a] (apo[a]) to human fibronectin (Fn). To pursue those observations, we prepared, by both elastase digestion and recombinant technology, subsets of F2 of a different length containing either kringle (K) V or the protease domain (PD). We also studied rhesus monkey apo[a], which is known to contain PD but not KV. In the case of Fn, we used both an intact product and its tenth type III module (10FN-III) expressed in Escherichia coli. The binding studies carried out on microtiter plates showed that the affinity of F2 for immobilized 10FN-III was approximately 6-fold higher than that for Fn (dissociation constants = 1.75 +/- 0.31 nM and 10.25 +/- 1.62 nM, respectively). The binding was also exhibited by rhesus apo[a] and by an F2 subset containing the PD linked to an upstream microdomain comprising KIV-8 to KIV-10 and KV, inactive by itself. Competition experiments on microtiter plates showed that both Fn and 10FN-III, when in solution, are incompetent to bind F2. Together, our results indicate that F2 binds to immobilized 10FN-III more efficiently than whole Fn and that the binding can be sustained by truncated forms of F2 that contain the catalytically inactive PD linked to an upstream four K microdomain.
Edelstein
Celina
C
Department of Medicine, University of Chicago, Chicago, IL 60637, USA.
Yousef
Mohammed
M
Scanu
Angelo M
AM
D000595:Amino Acid Sequence; D000818:Animals; D001054:Apolipoproteins A / Q000737:chemistry* / Q000378:metabolism*; D005353:Fibronectins / Q000737:chemistry* / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008253:Macaca mulatta; D008969:Molecular Sequence Data; D010196:Pancreatic Elastase / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary
D001054:Apolipoproteins A; D005353:Fibronectins; D010196:Pancreatic Elastase