User:Tannerhoole/sandbox

Final Version
Myosin V Myosin V is an unconventional myosin motor, which is processive as a dimer and has a step size of 36 nm. It translocates (walks) along actin filaments traveling towards the barbed end (+ end) of the filaments. Myosin V is involved in the transport of cargo (e.g. RNA, vesicles, organelles, mitochondria) from the center of the cell to the periphery, but has been furthermore shown to act like a dynamic tether, retaining vesicles and organelles in the actin-rich periphery of cells. A recent single molecule in vitro reconstitution study on assembling actin filaments suggests that Myosin V travels farther on newly assembling (ADP-Pi rich) F-actin, while processive runlengths are shorter on older (ADP-rich) F-actin.

ADDITION

The Myosin V motor head can be subdivided into the following functional regions:
 * Nucleotide-binding site - These elements together coordinate di-valent metal cations (usually magnesium) and catalyze hydrolysis:
 * Switch I - This contains a highly conserved SSR motif. Isomerizes in the presence of ATP.
 * Switch II - This is the Kinase-GTPase version of the Walker B motif DxxG. Isomerizes in the presence of ATP.
 * P-loop - This contains the Walker A motif GxxxxGK(S,T). This is the primary ATP binding site.


 * Transducer - The seven β-strands that underpin the motor head's structure.
 * U50 and L50 - The Upper (U50) and Lower (L50) domains are each around 50kDa. Their spatial separation forms a cleft critical for binding to actin and some regulatory compounds.
 * SH1 helix and Relay - These elements together provide an essential mechanism for coupling the enzymatic state of the motor domain to the powerstroke-producing region (converter domain, lever arm, and light chains).
 * Converter - This converts a change of conformation in the motor head to an angular displacement of the lever arm (in most cases reinforced with light chains).

EXPLANATION

Added a substantial amount of information regarding the Myosin V motor head. The edit begins “The Myosin V motor head can be subdivided into the following functional regions:” and then proceeds to provide information on some of the more interesting (and general to other motor heads) regions of the Myosin V motor head. Added references and links to other Wikipedia pages to support the addition. ~Tannerhoole