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Steady-state intrinsic tryptophan fluorescence and circular dichroism spectroscopy are used to investigate the conformation of the acidic Q-rich region. The findings support a role for protein folding in the aryl hydrocarbon receptor (AhR) action and suggest possible mechanisms of receptor-dependent gene activation.

The interaction of nitric oxide with cytochrome P450 BM3 from Bacillus megaterium is analyzed by spectroscopic techniques and enzyme assays in order to identify nitrated tyrosine residue(s) in the enzyme. Nitric oxide ligates tightly to the ferric heme iron, inducing large changes in each of the main visible bands of the heme and inhibiting the fatty acid hydroxylase function of the protein.

Research has been conducted on the nematode polyprotein allergens/antigens. The role of these nematode signature amino acids has been investigated by altering them chemically or mutationally, concentrating on the ABA-1 allergen of the nematode Ascaris, and the results indicate that mutational alterations affect the protein stability.

The ABA-1 allergen protein of the parasitic nematode Ascaris suum is characterized using a fluorescent fatty acid analogue. It is predicted that the ABA-1 family of proteins consists of fatty acid and retinoid binding proteins with a common structural pattern based on a four-helix structure. Homologues of ABA-1 which act as important antigens in a number of parasitic nematodes were also observed to share the same properties. It is also distinguished from the family of small lipid binding proteins.

Conformational studies on four forms of the plasminogen activator inhibitor (PAI-1), the active and latent wild-type forms, the substrate mutant and its cleaved form, reveal the 50% denaturation of latent PAI-1 at 70 degrees Celsius, implying this form to be more stable than the active and substrate forms. The cleaved substrate exhibits good stability toward thermal and guanidinium chloride-induced unfolding. There are more changes in conformation during cleavage than during the transition from the active to latent form.

Vibrational Raman optical activity (ROA) and ultraviolet circular dichroism (UV CD) are used for studying the binding of divalent copper ions to the full-length recombinant murine prion protein Pr[P.sup.23-231] at neutral pH. The different impact of [Cu.sup.2+] and [Mn.sup.2+] ions on prion protein structure has originated in the different stability constants and geometries of their complexes.

The binding of divalent copper ions to the full-length recombinant murine prion protein PrP23-231 at neutral pH was studied using vibrational Raman optical activity (ROA) and ultraviolet circular dichroism (UV CD). The effect of the Cu2+ ions on PrP structure depends on whether they are added after refolding of the protein in water or are present during the refolding process. In the first case ROA reveals that the hydrated alpha-helix is lost, with UV CD revealing a drop from approximately 25% to approximately 18% in the total alpha-helix content. The lost alpha-helix could be that comprising residues 145-156, located within the region associated with scrapie PrP formation. In the second case, ROA reveals the protein's structure to be almost completely disordered/irregular, with UV CD revealing a drop in total alpha-helix content to approximately 5%. Hence, although Cu2+ binding takes place exclusively within the unfolded/disordered N-terminal region, it can profoundly affect the structure of the folded/alpha-helical C-terminal region. This is supported by the finding that refolding in the presence of Cu2+ of a mutant in which the first six histidines associated with copper binding to the N-terminal region are replaced by alanine has a similar alpha-helix content to the metal-free protein. In contrast, when the protein is refolded in the presence of divalent manganese ions, ROA indicates the alpha-helix is reinforced, with UV CD revealing an increase in total alpha-helix content to approximately 30%. The very different influence of Cu2+ and Mn2+ ions on prion protein structure may originate in the different stability constants and geometries of their complexes.