Luciferase FMN complex- Vibrio harveyi: Difference between revisions

<StructureSection load='3fgc' size='400' side='right' caption='Structure of Bacterial Luciferase and FMN, phosphate and sulfate complex from V. harveyi (PDB entry [[3fgc]])' scene=''>

Luciferase found in '''V. Harveyi''' binds noncovalently to a reduced flavin mononucleotide cofactor, an aliphatic aldehyde and oxygen to yield  oxidized flavin mononucleotide, water, and carboxylic acid. The reaction occurs in two steps forming a hydroxyflavin intermediate and ultimately results in the oxidation of the aldehyde and emission of photons<ref Campbell, Z.T.>PMID: 19435287</ref>.  

<p>'''The &#946; subunit''': The beta subunit is characterized as a necessary but non-catalytic subunit that stabilizes the catalytic &#945; subunit that is responsible for the oxidation reaction.  The beta and alpha subunits are connected by a single interaction between the <scene name='User:Mitchell_Long/Sandbox_1/Phe272_tyr151_interface/1'>Phe 272 Tyr 151 interface</scene>

<p>'''Mobile Loop''': Residues 272-288 on the &#945; are known as the mobile loop.  This portion of the alpha subunit contains a single residue that forms a salt bridge with the beta subunit and stabilizes the active site<ref Campbell, Z.T.>PMID: 19435287</ref>.

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.