The layered organization of nucleosomes in 30 nm chromatin fibers.
We have used electron microscopy and established methods of three-dimensional reconstruction to obtain structural information on the 30 nm chromatin fibers from sea cucumber sperm and chicken erythrocytes. The fibers show a longitudinal periodicity of 10-11 nm. We have interpreted this periodicity as due to a grouping of nucleosomes into disks, each disk containing about 5-6 nucleosomes. These disks are closely stacked to form the chromatin fiber. We have built a detailed model for four fibers and we have determined the approximate coordinates of all the nucleosomes in them. The average distance found between neighboring nucleosomes has a value close to 11 nm. They may be connected either as a regularly distorted helix or as a layered zigzag. The second model appears more appropriate, since in the constrictions of the fibers the nucleosomes can only be connected as a zigzag.
D000818:Animals; D002645:Chickens; D002843:Chromatin / Q000648:ultrastructure*; D004912:Erythrocytes / Q000648:ultrastructure; D008297:Male; D008854:Microscopy, Electron; D009707:Nucleosomes / Q000648:ultrastructure*; D012616:Sea Cucumbers; D013094:Spermatozoa / Q000648:ultrastructure
D002843:Chromatin; D009707:Nucleosomes