In healthy red blood cells (RBCs), myosin fibers (blue) contract, pulling on actin (pink) and spectrin proteins (purple) connected to the cell membrane and helping to give the cells their distinct, indented shape (below, top panel). When the myosin fiber is experimentally manipulated so that it slackens or detaches from the cell-membrane proteins, red blood cells instead take on an oval shape (bottom panel).
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