Chromomycin A3
# Chromomycin A3

Chromomycin A3 $(CMA_3)$ or Toyomycin is an anthraquinone antibiotic glycoside produced by the fermentation of a certain strain of Streptomyces griseus (No. 7).

## Fluorescence properties

In the presence of $Mg^{2+}$ ions, Chromomycin $A_3$ binds reversibly to DNA, preferentially to contiguous G/C base pairs.

When bound to DNA, Chromomycin $A_3$ has a maximum excitation wavelength of 445 nm (blue), and a maximum emission wavelength of 575 nm (yellow).

## Uses

* in-vitro membrane-impermeant G/C-specific fluorescent DNA-binding dye.
* in-vitro antibiotic of gram-positive bacteria, through inhibition of the incorporation of $P_i$ in the RNA.
* in-vitro anticancer drug that inhibits RNA synthesis.
* Evaluation of male fertility: Chromomycin $A_3$ and protamines compete for the same binding sites in the DNA, so $CMA_3$ positivity in spermatozoa reflects protamine deficiency (affecting sperm morphology and decreasing fertility).
