Structure and function of annexin V-decorsin fusion

Decorsin is an antagonist of fibrinogen receptor on platelets and Annexin V is able to recognize stimulated platelets. Two recombinant proteins, Annexin V plus Decorsin (AnnV-D39) and Annexin V plus the C terminal 27 amino acids variant of Decorsin (AnnV-D27), were constructed, expressed, and purified. Platelet Aggregation assay results appear that AnnV-D39 shows good anti-platelet aggregation activity, but AnnV-D27 no such activities in any platelet aggregation assay test. And computational simulations reveal that AnnV-D39 showed good anti-platelet aggregation activity as a new antagonist of fibrinogen receptor, while Annv-D27 needs re-modification. Despite the AnnV_D39 fusion is more than decorsin, the former maintains the binding sites of decorsin interacton with its receptor, which contains Asp10, Arg28-Asp33, and Tyr37-Glu39. And the addition of Annexin V could not influence the interaction between its decorsin part with its receptor GPIIb-IIIa due to the linkage peptide (GGGGSGGGGS). Although the AnnV_D27 fusion is similar to the AnnV_D39 fusion, there are differences between them, where the former is in shortage of the linkage peptide and the N-terminal segment of decorsin whose one residue (Asp10) contribution to its interaction with GPIIb-IIIa. Meanwhile, these complex models suggest that decorsin plays a role in antiplatelet aggregation not only by its RGD motif interaction with its GPIIb-IIIa receptor, but also by other residues, especially Asp10 of its N-terminal segment and Tyr37-Glu39 of its C-terminal segment. On the other hand, the linkage peptide acts as avoidance of influence and blockage between domains of fusion. This is the cause that AnnV-D39 shows good anti-platelet aggregation activity.