Herbimycin A is a benzoquinone ansamycin antibiotic from Streptomyces. It has herbicidal activity and acts as a cell-permeable inhibitor of non-receptor tyrosine kinases and the heat shock protein Hsp90. Herbimycin A inhibits Bcr-Abl with an IC50 value of 5 μM, a concentration that also effectively blocks Src, Yes, Fps, Ros, and ErbB but not protein kinases (PK) PKA, PKC, Rac, Myc, or Raf. Presumably through its effects on tyrosine kinase signaling, herbimycin A also impairs endothelial cell proliferation in the context of angiogenesis, NF-κB activation, phosphorylation of phospholipase C-γ1, and eggshell formation in schistosome parasites. Ansamycins, including herbimycin A and geldanamycin , bind Hsp90 and destabilize client proteins, including Src, Bcr-Abl, and ErbB2, leading to their ubiquitination and proteasomal degradation.
