Summary of 2-headed & mask motif structures.

Values are calculated as: (number of structures)/(number of repeats) * 100. Because a single repeat might have two 2-headed bridges, the theoretical maximum is 200% (as seen in rigor). The same argument applies to mask motifs. 1Includes all two-headed or mask motif attachments. 2Means both heads are strong attachments. 3The mean lever arm axial angle of heads bound to target zone actin subunits H and I on the M-ward side compared with that on actin subunits J and K on the Z-ward side. 4Indicates both attachments occur on target zone actins H-K.