The sequences of Ca2+-binding site 2 in CRDs of CfLec-4 were diversified. Functional differentiation was observed among the CRDs of CfLec-4. CRD3 and CRD4 were the dominant CRDs for CfLec-4's PAMP recognition. CRD1, CRD3 and CRD4 contributed mainly for opsonization triggered by CfLec-4.