Luciferase FMN complex- Vibrio harveyi: Difference between revisions

Luciferases are a class of enzymes that catalyze the oxidation of a long chain aliphatic aldehydes and emit photons.  The luciferase found in [http://en.wikipedia.org/wiki/Vibrio_harveyi Vibrio harveyi] is a heterodimer that is composed of a catalytic α subunit and a homologous but noncatalytic β subunit.  This reaction results in the formation of a carboxylic acid, reduced flavinmononucleotide and the emission of photons in the form of blue-green light.  The catalytic α subunit houses the active site and is connected to the β subunit via a single interatcion between the mobile loop and the α subunit at α Phe 272 and Tyr 151 of the β subunit.   

In a process known as quorum sensing, bacteria communicate using secreted signal molecules called autoinducers(AIs). ''''V. harveyi'''' is a mesophilic, gram negative, rod shaped bacteria that can communicate with other bacteria via quorum sensing.  Quorum-sensing bacteria alter gene expression in response to the accumulation of AIs, which reflects an increase in cell population density<ref name=Waters, C.M.>PMID: 17015436</ref>. This process is believed to provide bacteria a means to coordinately control the gene expression of the group, giving them multicellular characteristics. When bacteria reach a "quorum," their population has reached a density high enough to coordinate gene expression<ref name=Waters, C.M.>PMID: 17015436</ref>. Often, bacteria make and respond to multiple AIs. Vibrio harveyi, a free-living marine bacterium, produces at least three distinct AIs to control bioluminescence, biofilm formation, Type III Secretion (TTS), and protease production. When a bacterial population density is low, the LuxI gene is transcribed constitutively at basal level.  The three V. harveyi AIs are HAI-1, an acyl homoserine lactone; AI-2, a furanosyl-borate-diester; and CAI-1, of unknown structure<ref name=Waters, C.M.>PMID: 17015436</ref>.  When the population density reaches an adequate level, the conjugate receptor LuxR begins transcription.  LuxR is the regulatory receptor, and when an AI binds the the LuxR receptor,  transcription is turned on resulting in the production of more AI and the expression of other genes involved in quorum sensing.  When '''V. harveyi''' reaches a high enough population density, it's quorum sensing genes are activated and the transcription of the genes that code for the luciferase enzyme.