Fourier transform IR and Fourier transform Raman spectroscopy studies of metallothionein‐III: Amide I band assignments and secondary structural comparison with metallothioneins‐I and ‐II

The secondary structures of porcine brain Cu 4 Zn 3 ‐metallothionein (MT)‐III and Cd 5 Zn 2 MT‐I, Cd 5 Zn 2 MT‐II, and Zn 7 MT‐I from rabbit livers in the solid state are investigated by Fourier transform IR spectroscopy (FTIR) and Fourier transform Raman spectroscopy (FT‐Raman). The Cu 4 Zn 3 MT‐III contains 26–28% β‐turns and half‐turns, 13–14% 3 10 ‐helices, 47–49% random coils, and 11–12% β‐extended chains. The structural comparison of porcine brain Cu 4 Zn 3 MT‐III with rabbit liver Cd 5 Zn 2 MT‐I (II) and Zn 7 MT‐I shows that the contents of the random coil structure are obviously increased. The results indicate that the insert of an acidic hexapeptide in the α domain of Cu 4 Zn 3 MT‐III possibly forms an α helix. However, because the bands assigned to the α‐helix and random coil structures are overlapped in the spectra, the content of random coil structures in Cu 4 Zn 3 MT‐III is therefore higher than those in Cd 5 Zn 2 MT‐I, Cd 5 Zn 2 MT‐II, and Zn 7 MT‐I. © 2002 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 65: 81–88, 2002