The molecular architecture of axonemes revealed by cryoelectron tomography.
Eukaryotic flagella and cilia are built on a 9 + 2 array of microtubules plus >250 accessory proteins, forming a biological machine called the axoneme. Here we describe the three-dimensional structure of rapidly frozen axonemes from Chlamydomonas and sea urchin sperm, using cryoelectron tomography and image processing to focus on the motor enzyme dynein. Our images suggest a model for the way dynein generates force to slide microtubules. They also reveal two dynein linkers that may provide "hard-wiring" to coordinate motor enzyme action, both circumferentially and along the axoneme. Periodic densities were also observed inside doublet microtubules; these may contribute to doublet stability.
Nicastro
Daniela
D
Laboratory for 3D Electron Microscopy of Cells, Department of Molecular, Cellular, and Developmental Biology, CB 347, University of Colorado, Boulder, CO 80309-0347, USA. nicastro@colorado.edu
Schwartz
Cindi
C
Pierson
Jason
J
Gaudette
Richard
R
Porter
Mary E
ME
McIntosh
J Richard
JR
D000818:Animals; D002352:Carrier Proteins / Q000737:chemistry / Q000648:ultrastructure; D016825:Chlamydomonas reinhardtii / Q000648:ultrastructure; D020285:Cryoelectron Microscopy; D004398:Dyneins / Q000737:chemistry* / Q000502:physiology / Q000648:ultrastructure*; D005407:Flagella / Q000737:chemistry / Q000502:physiology / Q000648:ultrastructure*; D005615:Freezing; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008297:Male; D008869:Microtubule-Associated Proteins; D008870:Microtubules / Q000737:chemistry / Q000502:physiology / Q000648:ultrastructure*; D008954:Models, Biological; D020409:Molecular Motor Proteins / Q000737:chemistry / Q000648:ultrastructure; D017434:Protein Structure, Tertiary; D012617:Sea Urchins; D013082:Sperm Tail / Q000737:chemistry / Q000502:physiology / Q000648:ultrastructure*; D014054:Tomography
D002352:Carrier Proteins; D008869:Microtubule-Associated Proteins; D020409:Molecular Motor Proteins; C484652:microtubule nexin; D004398:Dyneins