3.4.21.42	Ca2+	dependent on	752432, 755267	
3.4.21.42	Ca2+	recombinant CUB1-EGF-CUB2 region of enzyme C1s , dependent on, required for substrate binding. The CUB1-EGF-CUB2 domains of C1s are arranged linearly with three Ca2+: one in each CUB domain and one within the EGF-like domain, near the CUB1-EGF junction	732820	
3.4.21.42	Ca2+	the NH2-terminal alpha fragment of the enzyme contains one high affinity Ca2+ binding site	81399