Issue Date: April 16, 2007
T. rex fossil harbors ancient protein
A surprisingly well-preserved Tyrannosaurus rex leg bone has let loose some of its ancient protein, which researchers believe is collagen, a fibrous protein abundant in bone. When paleontologist Mary Higby Schweitzer of North Carolina State University and collaborators saw what appeared to be intact tissues in the 68 million-year-old dinosaur bone, collagen immediately came to mind. It had previously been identified in a 100,000- to 300,000-year-old mammoth bone—but that's much younger than their T. rex fossil. An amino acid profile revealed that one-third of the T. rex protein is glycine. This is telling because, in collagen, glycine is present at every third amino acid as a helical turn in the protein's structure (Science 2007, 316, 277). Atomic force microscopy measurements, hydroxylation, and antibody assays pointed to collagen too. But a clear-cut assignment required the sensitive ion-trap mass spectrometry of John M. Asara of Beth Israel Deaconess Medical Center, in Boston, and colleagues. They also report several sequences for the T. rex protein that are most closely related to modern chicken collagen (Science 2007, 316, 280).
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