Microribbons of the ventral disc are composed of three parallel sheets.

<p><b>A</b>) The bridge (B) connects the axis-facing sheet (A) to the side rail (SR). In addition, there is a complex array of proteins connecting the side-arm (SA) to the margin-facing sheet (M). The inner sheet (I) of the microribbon is partially associated with the margin-facing sheet. <b>B</b>) Lateral connections between the three sheets are evident (arrowheads). <b>C</b>) The axis-facing sheet has a distinct 16 nm repeat of 3 domains, one of which sticks out and is likely the attachment site of the crossbridges (CB) from the neighboring microribbon. <b>D</b>) A faint 5 nm repeat is evident along the dorsal-ventral line of the axis-facing sheet. <b>E</b>) The grand average isosurface has been inserted back into the original data, where each segment of the model has been rotated and shifted according to the parameters derived from the average. Dotted red lines have been drawn to indicate that the crossbridges on the margin-facing side likely connect to the 16 nm protrusions on the axis-facing side of the microribbon. Scale bars A–D, schematic = 5 nm, E = 25 nm.