Components of a "dynein regulatory complex" are located at the junction between the radial spokes and the dynein arms in Chlamydomonas flagella.

Abstract

Abstract. Previous studies of flagellar mutants have identified six axonemal polypeptides as components of a "dynein regulatory complex" (DRC). The DRC is thought to coordinate the activity of the multiple flagellar dyneins, but its location within the axoneme has been unknown Piperno et al., 1992). We have used improved chromatographic procedures (Kagami and Kamiya, 1992) and computer averaging of EM images (Mastronarde et al., 1992) three DRC mutants lack a crescent-shaped density above the second radial spoke, and pf3 axonemes lack additional structures adjacent to the crescent. We propose that the crescent corresponds in part to the location of the DRC, and that this structure is also directly associated with a subset of the inner dynein arms. This position is appropriate for a complex that is thought to mediate signals between the radial spokes and the dynein arms.

In Situ Localization of N and C Termini of Subunits of the Flagellar Nexin-Dynein Regulatory Complex (N-DRC) Using SNAP Tag and Cryo-electron Tomography

“…6), which is consistent with the biochemical data that DRC4 is reduced but not completely missing from pf3 axonemes (6). The location of parts of DRC4 to the N-DRC base plate is also consistent with previous observations that dynein e is reduced in pf2 axonemes (7,8,14). In our structural study, most of the nexin linker is missing in the A modified three-dimensional isosurface image shows the locations of the SNAP-biotinstrep-Au labels (gold) at the N and C termini of DRC3 and the C terminus of DRC4 in Chlamydomonas axoneme.…”

“…At least 11 proteins (DRC1-11) have been assigned to the N-DRC based on proteomic approaches (5)(6)(7). N-DRC mutations usually cause defective ciliary motility (8), and importantly, the lack of CCDC164 (DRC1) or CCDC65 (DRC2) has been identified as a cause of primary ciliary dyskinesia, a chronic human respiratory disease (9 -11). Knowledge of the precise locations of the individual components of the N-DRC and of their arrangement within the larger N-DRC structure is not yet available, but it is essential for a better understanding of the regulatory mechanism of the N-DRC.…”

The radial spokes and central apparatus: Mechano‐chemical transducers that regulate flagellar motility

“…It is not yet known if there are direct interactions between the radials spokes and dynein arm components. However, structural analyses indicate that the base of the spokes may be in a position to interact with subsets of inner dynein arms or components of the dynein regulatory complex (DRC) [Piperno et al, 1990[Piperno et al, , 1992Kagami and Kamiya, 1992;Gardner et al, 1994].…”

Molecular architecture of axonemal microtubule doublets revealed by cryo-electron tomography

“…For example, there are distinctive densities inside the regions where the dynein heads are located. The largest feature, on PFs A10-A12, sits inside the attachment region for nexin and the dynein regulatory complex with which it is associated [23][24][25][26] . The density we observe between PFs 12 and 13 is at the point where the radial spokes meet the doublets and may be part of their attachment.…”