Protein's structure lights the way.In 1961, Osamu Shimomura discovered a light-emitting protein in the jellyfish jellyfish, common name for the free-swimming stage (see polyp and medusa), of certain invertebrate animals of the phylum Cnidaria (the coelenterates). The body of a jellyfish is shaped like a bell or umbrella, with a clear, jellylike material filling most of the Aequorea aequorea. Four decades later, Shimomura, now at the Marine Biological Laboratory The Marine Biological Laboratory (MBL) is an international center for research and education in biology and ecology. Founded in 1888, the MBL is the oldest independent marine laboratory in the Americas, taking advantage of a coastal setting in the Cape Cod village of Woods Hole, in Woods Hole Woods Hole, uninc. village (1990 pop. 1,080) and seaport in the town of Falmouth, Barnstable co., SE Mass., at the southwestern extremity of Cape Cod. It is the departure point for nearby island resorts (Martha's Vineyard, Nantucket). , Mass., and his colleagues have finally teased out the crystal structure of this photoprotein, known as aequorin ae·quor·in n. A protein secreted by certain jellyfish that interacts with seawater to produce bioluminescent light. [New Latin Aequorea, jellyfish genus (from Latin aequoreus, . Aequorin glows blue when calcium ions bind to it, but it's more than just a pretty protein. Researchers frequently use it to trace the movement of calcium in cells. Calcium ions regulate many life processes, such as muscle contraction Noun 1. muscle contraction - (physiology) a shortening or tensing of a part or organ (especially of a muscle or muscle fiber) contraction, muscular contraction shortening - act of decreasing in length; "the dress needs shortening" and communication between nerve cells. The details of how aequorin generates its blue light have remained mysterious, however. New techniques yielding an extraordinarily pure sample of the photoprotein spurred the researchers on their way. The team mapped out aequorin's three-dimensional molecular structure by analyzing the way crystals of the protein reflect X rays. Scientists had already figured out the basic chemistry behind aequorin's glow. A part of aequorin called coelenterazine reacts with oxygen to produce coelenteramide and carbon dioxide carbon dioxide, chemical compound, CO2, a colorless, odorless, tasteless gas that is about one and one-half times as dense as air under ordinary conditions of temperature and pressure. , while emitting light. Yet no one knew how coelenterazine fits into aequorin or how calcium participates in the light-emitting reaction. With the new structure, "we've now got an actual picture where we can see how things are arranged," says coauthor James F. Head of Boston University School of Medicine Boston University School of Medicine (BUSM) is one of the graduate schools of Boston University. It is an American medical school located in the South End neighborhood of Boston, Massachusetts. . "But we're still speculating on how, when this binds calcium, it goes on to cause the light-emitting reaction." Head, Shimomura, and their colleagues report the findings in the May 18 NATURE. Head suggests that the new research could eventually lead to a family of glowing aequorinlike sensors. If scientists knew how to change the photoprotein appropriately, he says, they might be able to engineer new proteins that would emit light when binding other ions, such as lead, zinc, or manganese. Head says that in the more distant future, research might even develop similar photoproteins that glow when encountering more-complex molecules vital to biological processes. |
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