Thermal Stability of Two Heterotrimeric Molecular Forms of the Quantitatively Major Collagen from the Kuruma Prawn Muscle

Abstract

Thermal stability of the pepsin-solubilized Type AR-I collagen was estimated by monitoring the protease-induced degradation of helical domains by SDS-PAGE. The pepsin-solubilized Type AR-Ia collagen, designated as [α1(AR-I)]₃, denatured at 34.7°C. On the other hand, the α1(AR-I) and α2(AR-I) components in the mixture of the pepsin-solubilized Type AR-Ib and AR-Ic collagens, [α1(AR-I)]₂ α2(AR-I) and α1(AR-I)[α2(AR-I)]₂, respectively, showed transition midpoints of 33.5 and 33.8°C, respectively. From these results, the pepsin-solubilized Type AR-Ib and AR-Ic collagens were less stable to heat than the pepsin-solubilized Type AR-Ia collagen. In addition, the α2(AR-I) component in the intact Type AR-Ib and AR-Ic collagens in the residual fraction after alkali (0.1 N NaOH) extraction from muscular tissue showed an approximate transition midpoint of 37.9°C. These combined resultssuggest that the thermal stability of intact Type AR-Ib and AR-Ic collagens are considerably reduced by pepsin digestion which causes the removal of their telopeptides and change of their molecular properties such as molecular arrangement or solubility.