Figure 4. Intrinsic properties of CrSAS-6 enable cartwheel ring stacking.

(a) Average of 1,668 subtomograms of reconstituted eight-fold symmetrical cartwheels (top and side views). Note radial spokes merging two by two (side view, arrowheads). (b) Plot profile across average subtomogram side view (at red dashed line in a), showing average 7.6±0.5 nm periodicity of spokes close to the hub. (c) Cryo-ET of CrSAS-6_NL highlighting peripheral periodicity of spokes; the purple dashed line illustrates the region from which the quantification of periodicities shown on the right was extracted (n=55 peripheral elements, data extracted from two tomograms). Scale bars to correspond to 50 nm. (d) Experimental height distribution of CrSAS-6_NL reconstituted cartwheels smoothed with a running average of four (light blue); dotted line shows the mean (107±48 nm, n=1,039; data extracted from four tomograms). (e) Regression lines using distribution peaks ranging from 4 to 133.5 nm (a=16.8±0.9) and above (a=8.2±0.2). Peaks used are marked by grey arrows in d. Weighted dots represent the number of cartwheel at each peak.