SYMPOSIUM-IN-PRINT

Enzymatic activity of albumin shown by coelenterazine chemiluminescence

Bioluminescence, the emission of light from live organisms, occurs in 18 phyla and is the major communication system in the deep sea. It has appeared independently many times during evolution but its origins remain unknown. Coelenterazine bioluminescence discovered in luminous jellyfish is the most common chemistry causing bioluminescence in the sea, occurring in seven phyla. Sequence similarities between coelenterazine luciferases and photoproteins from different phyla are poor (often < 5%). The aim of this study was to examine albumin that binds organic substances as a coelenterazine luciferase to test the hypothesis that the evolutionary origin of a bioluminescent protein was the result of the formation of a solvent cage containing just a few key amino acids. The results show for the first time that bovine and human albumin catalysed coelenterazine chemiluminescence consistent with a mono-oxygenase, whereas gelatin and haemoglobin, an oxygen carrier, had very weak activity. Insulin also catalysed coelenterazine chemiluminescence and was increased by Zn(2+). Albumin chemiluminescence was heat denaturable, exhibited saturable substrate characteristics and was inhibited by cations that bound these proteins and by drugs that bind to human albumin drug site I. Molecular modelling confirmed the coelenterazine binding site and identified four basic amino acids: lys195, arg222, his242 and arg257, potentially important in binding and catalysis similar to naturally occurring coelenterazine bioluminescent proteins. These results support the 'solvent cage' hypothesis for the evolutionary origin of enzymatic coelenterazine bioluminescent proteins. They also have important consequences in diseases such as diabetes, gut disorders and food intolerance where a mono-oxygenase could affect cell surface proteins.

Bioluminescence in the sea

Bioluminescence spans all oceanic dimensions and has evolved many times--from bacteria to fish--to powerfully influence behavioral and ecosystem dynamics. New methods and technology have brought great advances in understanding of the molecular basis of bioluminescence, its physiological control, and its significance in marine communities. Novel tools derived from understanding the chemistry of natural light-producing molecules have led to countless valuable applications, culminating recently in a related Nobel Prize. Marine organisms utilize bioluminescence for vital functions ranging from defense to reproduction. To understand these interactions and the distributions of luminous organisms, new instruments and platforms allow observations on individual to oceanographic scales. This review explores recent advances, including the chemical and molecular, phylogenetic and functional, community and oceanographic aspects of bioluminescence.

Family of the green fluorescent protein: journey to the end of the rainbow

Members of the family of the Green Fluorescent Protein (GFP) are the only known type of natural pigments that are essentially encoded by a single gene, since both the substrate for pigment biosynthesis and the necessary catalytic moieties are provided within a single polypeptide chain. In sharp contrast to the state of knowledge just three years ago when GFP was the only known protein of its kind, a whole family of related proteins, exhibiting striking diversity of features have now been identified. This provides new possibilities for a variety of studies ranging from applied biotechnology to evolutionary ecology.

Can coelenterates make coelenterazine? Dietary requirement for luciferin in cnidarian bioluminescence

In the calcium-activated photoprotein aequorin, light is produced by the oxidation of coelenterazine, the luciferin used by at least seven marine phyla. However, despite extensive research on photoproteins, there has been no evidence to indicate the origin of coelenterazine within the phylum Cnidaria. Here we report that the hydromedusa Aequorea victoria is unable to produce its own coelenterazine and is dependent on a dietary supply of this luciferin for bioluminescence. Although they contain functional apophotoproteins, medusae reared on a luciferin-free diet are unable to produce light unless provided with coelenterazine from an external source. This evidence regarding the origins of luciferin in Cnidaria has implications for the evolution of bioluminescence and for the extensive use of coelenterazine among marine organisms.

Bacterial luminescence: luminescence mechanism with cyclic peroxide participation and dependence on reactive oxygen species (a hypothesis)

Chemically initiated exchange (CIEE) luminescence reactions were reviewed and a new mechanism of luminescence with peracid as an intermediate is proposed; bacterial luminescence is generally considered to be a case of dioxetane luminescence, or, to be more precise, CIEE-luminescence which includes the generation of a cyclic peroxide. In the hypothesis the monooxygenase reaction (aldehyde -->fatty acid) should not be coupled with emitter generation as is usually believed, but only with the generation of peracid. As to the generation of the emitter, excited flavin, it is likely to occur later, during the interaction of flavin with cyclic peroxide. Its consequence is the breaking of two chemical bonds (O-O and C-C) in the cyclic peroxide and simultaneous generation of 4alpha-hydroxyflavin in exited state. In general, the generation of light includes three stages: 1) the monooxygenase reaction and the concurrent production of peracid; 2) the conversion of peracid to cyclic peroxide; and 3) the interaction of cyclic peroxide with flavin (through the CIEE mechanism).