Insight into residues critical for antithrombin function from analysis of an expanded database of sequences that includes frog, turtle, and ostrich antithrombins.

Complete sequences were determined for frog, turtle, and ostrich antithrombins. Protein sequence comparisons with the other 10 known antithrombin sequences and with sequences of other serpins have provided striking evidence for the conservation of the heparin activation mechanism and new insight into those residues important for heparin binding, for heparin activation, and for reactive center loop function, as well as an indication of which glycosylation sites might be needed for function. Importantly, an understanding of, as yet, poorly understood antithrombin-protein interactions will be greatly aided by this expanded database and comparative analysis.