Molecular cloning and biochemical characterization of the phospholipid scramblase SCRM-1 from Caenorhabditis elegans

In this study, the SCRM-1 gene from Caenorhabditis elegans was cloned and overexpressed in E. coli to study the biochemical properties of scramblase. This is the first report showing that this scramblase from C. elegans possesses a Ca²⁺-dependent and head group-independent scramblase activity. The SCRM-1 of C.elegans possesses functional domains including a single EF-hand-like Ca²⁺ binding domain, as human scramblases do. A point mutation in the EF-hand-like Ca²⁺ binding motif results in loss of scramblase activity. Other biochemical assays like carbocyanine staining, Tb³⁺ luminescence, Tryptophan fluorescence, and CD spectroscopy strongly proved the role of the EF-hand motif for functional activity. The increase in protein size in solution upon incubating with Ca²⁺ shows ligand-dependent oligomerization and conformational changes.