Homoserine lactone

Homoserine lactones are signaling chemicals involved in microbiological quorum sensing. They signal changes in gene expression, such as switching between the flagella gene and the gene for pili for the development of a biofilm.

In the presence of homoserine lactones, the operon luxAB is transcribed. These Lux genes are present in the chemiluminescent bacterium Vibrio fischeri, and similar operons are present in other bioluminescent bacteria. Transcription of the operon results in luminescence due to the expression of LuxA and LuxB, which form a protein known as luciferase.

It is also a product of the proteolytic reaction of cyanogen bromide (CNBR) with a methionine residue in a protein. This reaction is important in protein sequencing, as the Edman degradation process is unable to sequence more than 70 residues at a time.