But this evidence was still far from proving that barnacle glue cures by the same process as blood clots. Dickinson and Rittschof needed to identify the key proteins that polymerize the cement. Knowing that blood clots are formed when enzymes, known as trypsin-like serine proteases, trigger a cascade of events that culminates in the formation of the long fibres found in blood clots, Dickinson and Rittschoff began searching for the protease in the unpolymerised glue. Separating the glue's components on a gel, Dickinson could see the tell-tale pattern of bands that suggested that a trypsin-like serine protease was present. And when Dickinson added an inhibitor, to inactivate the protease, to a fresh sample of glue, the sample didn't set.
Having convinced themselves that the glue contained a trypsin-like serine protease, the team began to search for other blood-clot-like proteins in the barnacle's secretions. Teaming up with Joseph Bonaventura and Irving Vega, Dickinson chopped each glue component into minute fragments, measured their sizes with mass spectrometry and matched the fragment pattern to known protein sequences. Amazingly, one of the glue proteins was remarkably similar to human factor XIII: a human blood clotting factor that cross-links clot fibres to form a scab. In fact, some regions of the human and barnacle proteins were completely identical. Dickinson and Rittschof had stumbled across the crucial protein that cross-links the glue fibres to cure barnacle cement and it was very similar to factor XIII, an essential human blood-clotting factor.
Rittschof admits that he is shocked that his hypothesis stands up to the tests. 'It seems likely that barnacle glue polymerization is a specialized form of wound healing,' he says and s
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The Company of Biologists