Resumen de Ca2+ Affects Physicochemical and Conformational Changes of Threadfin Bream Myosin and Actin in a Setting Model
Bung-Orn Hemung, Jirawat Yongsawatdigul
The effect of Ca2+ on physicochemical and conformational changes of threadfin bream (TB) myosin and actin during setting at 25 and 40°C was investigated. Ca2+ ion at 10 to 100 mM induced the unfolding of myosin and actin as evident by an increase of surface hydrophobicity (So ANS) at 40 °C. Total SH groups also decreased with an increased Ca2+ concentration, suggesting that Ca2+ promoted the formation of disulfide bonds during setting at 40 °C. Both hydrophobic interactions and disulfide linkages were involved in formation of myosin aggregates at 40 °C and were enhanced by addition of 10 to 100 mM Ca2+. Myosin Ca-ATPase activity decreased when Ca2+ was greater than 50 mM, indicating conformational changes of myosin head. Circular dichroism spectra demonstrated that Ca2+ reduced the α-helical content of myosin and actin incubated at either 25 or 40 °C. Ca2+ induced conformational changes of TB myosin and actin incubated at 40 °C to a greater extent than at 25 °C.
