Muhl et al have -for the first time- produced recombinant FSAP and its variants, and studied the regulation of the proteolytic activity of FSAP.
Over-expression of enzymatically active FSAP in HEK-293 cells decreased the cell viability; FSAP seems to have an intracellular function in regulating cell death, possibly via its ability to bind nucleic acids. Expression of the naturally occuring Marburg I variant confirmed previous results with plasma-derived material that this variant has low enzymatic activity.
The hypothesis, that the EGF-3 domain is important for the activation of FSAP by polyanions was proven; a recombinant variant -lacking the EGF-3 domain- showed diminished binding to and activation by heparin.

Author and Source:
Muhl et al. FEBS Lett. 2009 Jun 18;583(12):1994-1998.

Title:
Structure – function analysis of FSAP: Sequence determinants for heparin binding and cellular functions

Comment:
The anti-FSAP antibodies used for these studies are available from American Diagnostica.