Tunicamycin

Tunicamycin is a mixture of closely related nucleoside antibiotics produced by several bacteria, including Streptomyces clavuligerus and Streptomyces lysosuperificus. It inhibits a family of enzymes that start the attachment of sugar units to lipid carriers, and in eukaryotic cells this includes GlcNAc phosphotransferase, which carries out the first step of glycoprotein synthesis. By blocking N-linked glycosylation it causes cultured human cells to stop dividing in the G1 phase of the cell cycle. Its main use is as an experimental tool in biology, for example to trigger the unfolded protein response, rather than as a medicine. The individual homologues in the mixture differ in molecular weight because their fatty acid side chains vary.