Homocysteine binds to human plasma fibronectin and inhibits its interaction with fibrin.
OBJECTIVE
More than 70% of circulating homocysteine is disulfide-bonded to protein, but little is known about the specific proteins that bind homocysteine and their function as a consequence of homocysteine binding.


RESULTS
When human plasma was incubated with [(35)S]L-homocysteine, most of the homocysteine bound to albumin. However, additional homocysteine-binding proteins were detected, and 1 of them comigrated with fibronectin. Treatment with 2-mercaptoethanol removed the bound homocysteine, demonstrating the involvement of disulfide bonding. In contrast, [35S]L-cysteine did not bind to fibronectin. Purified fibronectin bound approximately 5 homocysteine molecules per fibronectin dimer. SDS-PAGE of a limited trypsin digestion of homocysteinylated fibronectin showed that several tryptic fragments contained [35S]homocysteine. Sequence analysis demonstrated that the fragments containing bound homocysteine had localized mainly to the C-terminal region, within and adjacent to the fibrin-binding domain. Homocysteinylation of fibronectin significantly inhibited its capacity to bind fibrin by 62% (P<0.005). In contrast, neither the binding of fibronectin to gelatin nor its capacity to serve as an attachment factor for aortic smooth muscle cells was affected.


CONCLUSIONS
These results suggest that homocysteine may alter normal thrombosis and delay or interfere with wound healing by impairing the interaction of fibronectin with fibrin.
Majors
Alana K
AK
Department of Cell Biology, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.
Sengupta
Shantanu
S
Willard
Belinda
B
Kinter
Michael T
MT
Pyeritz
Reed E
RE
Jacobsen
Donald W
DW
D001161:Arteriosclerosis / Q000097:blood; D001667:Binding, Competitive; D005337:Fibrin / Q000378:metabolism*; D005353:Fibronectins / Q000097:blood* / Q000378:metabolism; D005780:Gelatin / Q000378:metabolism; D006710:Homocysteine / Q000097:blood*; D006801:Humans; D066298:In Vitro Techniques; D009131:Muscle, Smooth, Vascular / Q000378:metabolism; D013927:Thrombosis / Q000097:blood
D005353:Fibronectins; D006710:Homocysteine; D005780:Gelatin; D005337:Fibrin