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Research has been conducted on the activated factor VII (FVIIa) that forms a high-affinity complex with its allosteric regulator, tissue factor and initiates blood clotting. The interactions of the FVIIa and the active site-inhibited factor VIIa with the soluble tissue factor have been investigated and described.

The central part of the beta-sheet core, consisting of 10 beta-strands of the enzyme human carbonic anhydrase II, has an ordered native-like secondary structure, while the beta-sheet close to the surface is less ordered. The native state of an enzyme is attained via formation of intermediates by folding. Understanding the precise amino acid sequence required for the protein to fold into a specific three-dimensional conformation for biological activity is a challenge.

Two-dimensional NMR spectroscopic studies of the wild-type human carbonic anhydrase II and its mutants, resulting from the replacement of tryptophan residues by cysteine or phenylalanine, reveal no significant changes in protein structure. The two tryptophan residues, Trp 97 and Trp 245, contribute 52% and 38%, respectively, to the fluorescence spectrum. His64 quenches the fluorescence from Trp5, while there is a transfer of energy from Trp192 to Trp209 and from Trp16 to Trp5. The beta-strands 3-7 of the native protein correspond to the core of a globule intermediate, as revealed by a study of the tryptophan environment through acrylamide quenching of the fluorescence.

A study reports the activity, folding, and aggregation behavior of the R200W mutant of the 219-residue soluble extracellular domain of tissue factor [(sub s)TF(sub R200W)] compared to that of the wild-type protein [(sub s)TF(sub wt)]. The study concludes that the lowered activity for FX activation and the propensity of the mutant protein to misfold and aggregate, both would contribute to decreased coagulation activity in TF(sub R200W) carriers.

Human carbonic anhydrase II (HCA II) interacts weakly with GroEL at room temperature. Electron paramagnetic resonance (EPR) spectroscopy was employed to investigate HCA II cysteine mutants spin-labeled at selected positions to further study the interaction. Findings showed that protein-protein interactions can be specifically mapped by site-directed spin-labeling and EPR measurements. HCA II had to be unfolded to approximately the same extent as a GuHCl-induced molten-globule intermediate of the enzyme to interact with GroEL.