Figure 5.

Class averages of F-actin-aldolase motifs generally arranged in order of the Y-position of the lower crosslink. (a) The central slices of those class averages with an apparent pair of aldolase crosslinks. In some class average, e.g. 5–7, both left and right actin filaments were well resolved. For other classes, the left actin filament subunits are clearly resolved but the density of the right side actin filaments are blurred and the subunits poorly resolved. (b) Surface view of the same class average as shown in (a). When both aldolase molecules function as cross links, both left and right actin filaments are clearly resolved. For the other classes, only one of the pair of aldolase molecules appears to function as a cross-link with the other molecules binding only one of the actin filaments. Consequently, the detail in the right actin filament is poor and subunits are not well resolved. (c) Ten class averages of single aldolase crosslinks. In this case, all the right-side F-actins are poorly ordered. The 19^th class average (not shown) is very similar to the fourth from the left in rows (c) and (d). Note the progression up the filament of the cross-links even with the left side F-actin positioned identically in each image. (d) Surface view of the same class averages shown in (c).