Conformational differences between mouse contrapsin and .ALPHA.-1-antitrypsin as studied by ultraviolet absorption and circular dichroism spectroscopy.

Abstract

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 a-l-antitrypsin by UV absorption and CD spectroscopy. The two mouse inhibitors share a similar secondary structure, i.e., 24-29% a-helix, 31% /-sheet, and 10-11% /l-turn. The corresponding values for human a-l-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 a-l-antitrypsin.On the other hand, evidence is accumulated that the microenvironments of aromatic side chains are considerably different in mouse contrapsin and a-l-antitrypsin : (i) An unusual fine vibrational structure was seen in the UV absorption spectra of murine and human a-l-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 a-l-antitrypins.(iii) The above-mentioned bands in contrapsin were more susceptible to pH changes than those in a-l-antitrypsin.(iv) CD bands in contrapsin which may contain unresolved contributions from tyrosyl and tryptophanyl residues also markedly differed from those in the two a-l-antitrypsins. These differences were, however, largely diminished in the presence of 50 mM sodium dodecyl sulfate, suggesting that mouse contrapsin and a-l-antitrypsin have a similar structure in the presence of this perturbant. UV absorption ; CD spectra ; mouse contrapsin ; mouse a-l-antitrypsin a-1-Antitrypsin or a-1-protease inhibitor is a glycoprotein which is responsible for about 90% of the trypsin-inhibiting capacity of human serum, and which

A Serpin Released by an Entomopathogen Impairs Clot Formation in Insect Defense System

“…The recombinant Sc-SRP-6-fold was analysed by recording the CD spectrum. The far-UV CD spectra presented a broad negative region in the 208–222 nm range with a minimum peak at 222 nm proceeded by a shoulder at 208 nm (Figure 3B), which is highly similar to that reported for canonical serpins [37]. Based on a deconvoluted spectrum, it was calculated that the Sc-SRP-6 secondary structure contains 15–20% α-helices, 30–35% β-strands, 20–25% β-turns and 23% random coils, which is in agreement with values (22% α-helical and 35% β-strand) predicted by I-TASSER.…”

“…In silico and CD data suggested that recombinant Sc-SRP-6 has an identical fold as the mouse serpin trypsin inhibitor with a composition consisting of 24–29% α-helices, 31% β-sheets, and 10–11% β-turns [37] and of plasminogen activator inhibitor-1, which is composed of 29% α-helices, 19% β-strands, 24% β-turns, and 27% random coils [39] and differs from that of human α-1-antitrypsin, which is composed of 48% α-helices, 25% β-sheets, and 9% β-turns [37].…”

Biochemical Characterization of Anopheles gambiae SRPN6, a Malaria Parasite Invasion Marker in Mosquitoes

“…To test whether pH influences the conformation of the protein we determined the far ultraviolet (UV) circular dichroism spectra of recombinant SRPN6 at different pH. The canonical native serpin fold is composed of a mixture of α-helices, β-sheets, β-turns, and loops, presented as a minimum peak at 222 nm preceded by a shoulder at 208 nm in the far-UV CD spectra [57]–[59]. The far UV CD spectrum of SRPN6 is highly similar to that of reported serpins (Fig.…”