Detection of Human and Mouse COX4 by Western Blot. Western blot shows lysates of A431 human epithelial carcinoma cell line, HepG2 human hepatocellular carcinoma cell line, and NIH‑3T3 mouse embryonic fibroblast cell line. PVDF membrane was probed with 1 µg/mL of Mouse Anti-Human COX4 Monoclonal Antibody (Catalog # MAB6980) followed by HRP-conjugated Anti-Mouse IgG Secondary Antibody (Catalog # HAF007). For addtional reference, recombinant human COX4-I1 (5 ng/lane) and recombinant human COX4-I2 (2.5 ng/lane) were included. A specific band was detected for COX4 at approximately 18 kDa (as indicated). This experiment was conducted under reducing conditions and using Immunoblot Buffer Group 2.