Figure 3.

N2A—actin interaction eliminates low-force straightening of tandem Ig domains. (A) Passive sarcomere at slack length. (B) As the sarcomere is stretched passively beyond its slack length, the proximal tandem Ig segments unfold approximately to their contour length. (C) After the proximal tandem Ig segments have reached their contour length, further passive stretching extends the PEVK segment. (D) Upon activation, N2A titin binds to actin. (E) When the active sarcomere is stretched, only the PEVK segment (green) extends. Reproduced with permission from Nishikawa [21]. Copyright 2016, The Company of Biologists Ltd.