Histidine 67 is critical for the membrane binding of CXCL4L1. (A) Schematic representation of the amino acide sequences of CXCL4, CXCL4L1, or mutants. (B) In cellulo binding properties of CXCL4, CXCL4L1 and mutants to cell membranes. HEK293T cells were transfected with plasmids expressing CXCL4, CXCL4L1, or mutants. The amount of proteins associated with the membrane was determined using the human CXCL4-ELISA, which detects CXCL4, CXCL4L1, and all variants.