Single molecule study on the mechanical response of the sixth domain of adseverin

Adseverin is a member of the calcium-regulated gelsolin superfamily that can sever, cap and uncap actin filaments. Force will be generated when adseverin regulates the architecture of the actin cytoskeleton. Thus, the mechanical properties of adseverin should be investigated. In this work, we systematically studied the mechanical response of the sixth domain of adseverin (A6) in the absence and presence of different concentrations of calcium ions using single-molecule force spectroscopy (SMFS) based on atomic force microscopy (AFM) and magnetic tweezers (MT), respectively. AFM results showed that the A6 mainly unfolded in a two-state unfolding manner. By contrast, MT results showed that A6 mainly unfolded in a three-state unfolding pathway. The unfolding force of A6 gradually increased with increase in calcium concentration. In addition, the mechanical unfolding force of A6 was more likely to occur in a two-state manner at a higher external force.