CXCL1/GRO alpha, also known as KC in mouse and CINC-1 in rat, is a member of the CXC family of chemokines. Human CXCL1/GRO alpha is 107 amino acids (aa) in length with a predicted molecular weight of 11 kDa. The mouse and rat orthologs share 57% and 59% amino acid sequence identity with the human protein, respectively. Genome-wide analysis suggests that the protein encoded by the mouse Cxcl3 gene is homologous to human CXCL1/GRO alpha protein. Human CXCL1/GRO alpha can be cleaved into three isoforms CXCL1/GRO alpha (aa 4-73), CXCL1/GRO alpha (aa 5-73), and CXCL1/GRO alpha (aa 6-73) which show higher activity than the full length protein. CXCL1/GRO alpha is secreted by mast cells and macrophages whereupon it acts as a chemoattractant for neutrophils.