Radial spoke

Radial spoke

The radial spoke is a multi-unit protein structure found in the axonemes of eukaryotic cilia and flagella. Although experiments have determined the importance of the radial spoke in the proper function of these organelles, its structure and mode of action remain poorly understood.

Cellular location and structure

Radial spokes are T-shaped structures present inside the axoneme. Each spoke consists of a "head" and a "stalk," while each of these sub-structures is itself made up of many protein subunits. In all, the radial spoke is known to contain at least 17 different proteins, with 5 located in the head and at least 12 making up the stalk. The spoke stalk binds to the A-tubule of each microtubule outer doublet, and the spoke head faces in towards the center of the axoneme (see illustration at right).

Function

The radial spoke is known to play a role in the mechanical movement of the flagellum/cilium. For example, mutant organisms lacking properly functioning radial spokes have flagella and cilia that are immotile. Radial spokes also influence the cilium "waveform"; that is, the exact bending pattern the cilium repeats.

How the radial spoke carries out this function is poorly understood. Radial spokes are believed to interact with both the central pair microtubules and the dynein arms, perhaps in a way that maintains the rhythmic activation of the dynein motors. For example, one of the radial spoke subunits, RSP3, is an anchor protein predicted to hold another protein called protein kinase A (PKA). PKA would theoretically then be able to activate/inactivate the adjacent dynein arms via its kinase activity.

However, the identities and functions of the many radial spoke subunits are just beginning to be elucidated.

References

#Pinfen Yang, Dennis Diener, Joel Rosenbaum, and Winfield Sale "Localization of Calmodulin and Dynein Light Chain LC8 in Flagellar Radial Spokes," , Journal of Cell Biology, Volume 153, Number 6, June 11 2001. Entrez Pubmed|11402073

#Yang P, Diener DR, Yang C, Kohno T, Pazour GJ, Dienes JM, Agrin NS, King SM, Sale WS, Kamiya R, Rosenbaum JL, Witman GB "Radial spoke proteins of Chlamydomonas flagella," Journal of Cell Science 119, February 2006. Entrez Pubmed|16507594


Wikimedia Foundation. 2010.

Игры ⚽ Нужно решить контрольную?

Look at other dictionaries:

  • radial spoke — The structure that links the outer microtubule doublet of the ciliary axoneme with the sheath that surrounds the central pair of microtubules. The spokes are arranged periodically along the axoneme every 29nm, have a stalk about 32nm long and a… …   Dictionary of molecular biology

  • radial — ► ADJECTIVE 1) of or arranged like rays or the radii of a circle; diverging in lines from a common centre. 2) (also radial ply) (of a tyre) in which the layers of fabric have their cords running at right angles to the circumference of the tyre.… …   English terms dictionary

  • spoke — [1] ► NOUN 1) each of the bars or wire rods connecting the centre of a wheel to its rim. 2) each of a set of radial handles projecting from a ship s wheel. 3) each of the metal rods in an umbrella to which the material is attached. ● put a spoke… …   English terms dictionary

  • Spoke — A spoke is one of some number of rods radiating from the center of a wheel (the hub where the axle connects), connecting the hub with the round traction surface. The term originally referred to portions of a log which had been split lengthwise… …   Wikipedia

  • Radial — In skeletal anatomy, radial refers to the radius, the smaller of the two bones on the thumb side of the forearm. (The bigger bone in the forearm is the ulna). In ophthalmology, a radial keratotomy is a procedure in which incisions (cuts) are made …   Medical dictionary

  • spoke — 1. n. & v. n. 1 each of the bars running from the hub to the rim of a wheel. 2 a rung of a ladder. 3 each radial handle of the wheel of a ship etc. v.tr. 1 provide with spokes. 2 obstruct (a wheel etc.) by thrusting a spoke in. Phrases and idioms …   Useful english dictionary

  • spoke — spoke1 noun 1》 each of the bars or wire rods connecting the centre of a wheel to its rim. 2》 each of a set of radial handles projecting from a ship s wheel. 3》 each of the metal rods in an umbrella to which the material is attached. Phrases put a …   English new terms dictionary

  • wheel spoke — noun support consisting of a radial member of a wheel joining the hub to the rim • Syn: ↑spoke, ↑radius • Hypernyms: ↑support • Part Holonyms: ↑bicycle wheel, ↑cartwheel, ↑wagon wheel …   Useful english dictionary

  • RSHL1 — Radial spokehead like 1, also known as RSHL1, is a human gene.cite web | title = Entrez Gene: RSHL1 radial spokehead like 1| url = http://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene Cmd=ShowDetailView TermToSearch=81492| accessdate = ] PBB Summary… …   Wikipedia

  • Wheelbuilding — is the art and science of assembling a wheel (generally a bicycle wheel, although such wheels are also used on wheelchairs, motorcycles, and some cars, and known as wire wheels) from its component rim, spokes, nipples and hub.GoalsA good… …   Wikipedia

Share the article and excerpts

Direct link
… Do a right-click on the link above
and select “Copy Link”