UC San Diego

The photoprotein of marine polychaete, Chaetopterus variopedatus, has been under investigation for decades because of its unique long-lasting light production ability and the potential of utilization in biochemical research as a reporter molecule. However, the exact light-producing mechanism remains unknown except that Fe2+ acts as the cofactor for the photoprotein. The goal of this thesis is to investigate this bioluminescence reaction pathway and to hopefully extract the previously unknown photoprotein. we discovered a preliminary relationship between

Fe2+ (photoprotein cofactor) concentration and mucus bioluminescence—a stimulation-inhibition dose response curve where ferrous iron stimulates light at a low concentration (£ 0.1 mM added) and starts to inhibit light as concentration increases (> 0.1 mM). Evidence suggests that Co2+ and Zn2+ are both competitive inhibitors for binding to the cofactor site on photoprotein and for bioluminescence. Co2+ has a stronger affinity than Fe2+ while Zn2+ has a lower affinity compared to Fe2+. We were able to purify Fe2+ binding protein from the mucus complex using Fe2+-affinity column. By using Co2+ as a substitute cofactor, we extracted from the mucus a light-inducing protein (37 kDa), which is a potential candidate for photoprotein or a protein that plays a role in the light production pathway.