Radial spoke proteins of Chlamydomonas flagella.
The radial spoke is a ubiquitous component of '9+2' cilia and flagella, and plays an essential role in the control of dynein arm activity by relaying signals from the central pair of microtubules to the arms. The Chlamydomonas reinhardtii radial spoke contains at least 23 proteins, only 8 of which have been characterized at the molecular level. Here, we use mass spectrometry to identify 10 additional radial spoke proteins. Many of the newly identified proteins in the spoke stalk are predicted to contain domains associated with signal transduction, including Ca2+-, AKAP- and nucleotide-binding domains. This suggests that the spoke stalk is both a scaffold for signaling molecules and itself a transducer of signals. Moreover, in addition to the recently described HSP40 family member, a second spoke stalk protein is predicted to be a molecular chaperone, implying that there is a sophisticated mechanism for the assembly of this large complex. Among the 18 spoke proteins identified to date, at least 12 have apparent homologs in humans, indicating that the radial spoke has been conserved throughout evolution. The human genes encoding these proteins are candidates for causing primary ciliary dyskinesia, a severe inherited disease involving missing or defective axonemal structures, including the radial spokes.
Yang
Pinfen
P
Department of Biological Sciences, Marquette University, Milwaukee, WI 53233, USA. pinfen.yang@marquette.edu
Diener
Dennis R
DR
Yang
Chun
C
Kohno
Takahiro
T
Pazour
Gregory J
GJ
Dienes
Jennifer M
JM
Agrin
Nathan S
NS
King
Stephen M
SM
Sale
Winfield S
WS
Kamiya
Ritsu
R
Rosenbaum
Joel L
JL
Witman
George B
GB
D000595:Amino Acid Sequence; D000818:Animals; D002696:Chlamydomonas / Q000378:metabolism* / Q000648:ultrastructure; D015180:Electrophoresis, Gel, Two-Dimensional; D005407:Flagella / Q000378:metabolism*; D050956:HSP40 Heat-Shock Proteins / Q000235:genetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010940:Plant Proteins; D015800:Protozoan Proteins / Q000032:analysis / Q000235:genetics / Q000302:isolation & purification; D017386:Sequence Homology, Amino Acid
D050956:HSP40 Heat-Shock Proteins; D010940:Plant Proteins; D015800:Protozoan Proteins; C060324:radial spoke protein, Chlamydomonas