GRO beta is a member of the CXC, or chemokine class. It contains the ELR domain immediately preceding the first cysteine residue near the amino terminus. Other chemokines in this group include IL8, GRO alpha/beta/gamma, mouse KC, ENA78, GCP2, PBP/CTAPIII/beta TG/NAP2. These chemokines act primarily on neutrophils as chemoattractants and activators, including neutrophil degradation with release of myloperoxidase and other enzymes. GRO beta was originally identified as a heparin-binding protein secreted from a murine macrophage cell line in response to endotoxin stimulation. GRO beta is an approximately 8 kDa polypeptide of 73 amino acids. The precursor form of GRO beta consists of 100 amino acids. To generate the mature GRO beta, the precursor cleaves its amino terminal 27 amino acids. GRO beta shows 60% amino acid homology to human GRO alpha and GRO gamma.