The esperamicins are a class of bacteria-derived chromoprotein

Chromoprotein

Chromoprotein: A conjugated protein, sulch as hemoglobin, that contains a pigmented prosthetic group, such as hem in hemoglobin . Other examples of chromoprotein are: myoglobin, cytochromes and flavoproteins.In hemoglobin:...

 enediyne

Enediyne

Enediynes are a class of bacterial natural products characterized by either nine- and ten-membered rings containing two triple bonds separated by a double bond. Many of these compounds are capable of undergoing Bergman cyclization...

 antibiotic

Antibiotic

An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...

s, of which esperamicin A1 is the most well studied. Esperamcin A1 and the related enediyne calicheamicin

Calicheamicin

The calicheamicins are a class of enediyne antibiotics derived from the bacterium Micromonospora echinospora, with calicheamicin γ1 being the most notable. It was isolated originally from a rock collected by a Scripps Research Institute chemist while hiking in Waco, Texas. It is extremely toxic to...

 are the two most potent antitumor agents known. The esperamicins are extremely toxic DNA splicing compounds.

Oxygen and oxygen scavengers have no significant effect on DNA breakage. The cleavage of DNA by esperamicin is greatly accelerated in the presence of thiol

Thiol

In organic chemistry, a thiol is an organosulfur compound that contains a carbon-bonded sulfhydryl group...

 compounds. Oxygen and active oxygen-radical scavengers have no significant influence upon DNA strand breakage by esperamicin. The preferential cutting sites of esperamicin are at thymidylate residues, and the frequency of nucleobase

Nucleobase

Nucleobases are a group of nitrogen-based molecules that are required to form nucleotides, the basic building blocks of DNA and RNA. Nucleobases provide the molecular structure necessary for the hydrogen bonding of complementary DNA and RNA strands, and are key components in the formation of stable...

 attacked (T greater than C greater than A greater than G) is different from that of calicheamicin (C much greater than T greater than A = G), neocarzinostatin

Neocarzinostatin

Neocarzinostatin is a macromolecular chromoprotein enediyne antibiotic with anti-tumoral activity secreted by Streptomyces macromomyceticus....

 (T greater than A greater than C greater than G), or bleomycin

Bleomycin

Bleomycin is a glycopeptide antibiotic produced by the bacterium Streptomyces verticillus. Bleomycin refers to a family of structurally related compounds. When used as an anticancer agent, the chemotherapeutical forms are primarily bleomycin A2 and B2. It works by causing breaks in DNA...

(C greater than T greater than A greater than G.