Abstract
TAKAHARA, H., SHIBATA, S. and SINOHARA, H., Conformational Differences between Mouse Contrapsin and α-1-Antitrypsin as Studied by Ultraviolet Absorption and Circular Dichroism Spectroscopy. Tohoku J. exp. Med., 1984, 142 (3), 261-273 - We have compared the conformation of mouse contrapsin, a novel trypsin inhibitor (Takahara, H. and Sinohara, H. (1982) J. biol. Chem., 257, 2438-2446), and α-1-antitrypsin by UV absorption and CD spectroscopy. The two mouse inhibitors share a similar secondary structure, i.e., 24-29% α-helix, 31% β-sheet, and 10-11% β-turn. The corresponding values for human α-1-antitrypsin are 48, 25, and 9%, respectively. These results suggest that peptide backbone structures of the two mouse inhibitors resemble each other, but differ slightly from that of human α-1-antitrypsin. On the other hand, evidence is accumulated that the microenvironments of aromatic side chains are considerably different in mouse contrapsin and α-1-antitrypsin: (i) An unusual fine vibrational structure was seen in the UV absorption spectra of murine and human α-1-antitrypsins, but not in that of contrapsin. (ii) CD bands in contrapsin which may be assigned to phenylalanyl residues were several-fold greater in intensity than those in the two α-1-antitrypsins. (iii) The above-mentioned bands in contrapsin were more susceptible to pH changes than those in α-1-antitrypsin. (iv) CD bands in contrapsin which may contain unresolved contributions from tyrosyl and tryptophanyl residues also markedly differed from those in the two α-1-antitrypsins. These differences were, however, largely diminished in the presence of 50mM sodium dodecyl sulfate, suggesting that mouse contrapsin and α-1-antitrypsin have a similar structure in the presence of this perturbant.
