Fourier transform infrared absorption studies on the sulfhydryl groups in heavy meromyosin

Infrared absorptions of heavy meromyosin solutions were studied in the frequency range of 2600 cm-1 to 1800 cm-1 with a Fourier transform infrared spectrophotometer. An absorption band characteristic of the stretching vibration of sulfhydryl groups was found at about 2565 cm-1. By comparison with the infrared absorption spectrum of a cysteine solution, the absorption band of sulfhydryl groups in heavy meromyosin showed that the absorption intensity is much stronger, the absorption peak shifts to a lower wavenumber and the width of the absorption band is much broadened. These results indicate that the sulfhydryl groups in heavy meromyosin are strongly hydrogen-bound. The additions of ATP and ADP increased the absorption intensity of the absorption band, suggesting the that hydrogen-bonded structure involving the sulfhydryl groups becomes more strengthened on the binding of ATP and ADP. This indicates that myosin heads change conformation around the sulfhydryl groups during ATP hydrolysis.