Kinesin-1 as Prototypical Motor

The first structure of a kinesin motor domain—that of human kinesin-l (formerly named KHC or conventional kinesin )—was determined by Kull and coworkers (1996). This is still the structure of highest resolution (1.8 A PDB code 1BG2) among all structures of conventional kinesins 

The central /1-sheet is the supporting structure for all the other structural elements and moving parts of the motor domain. Most of the central /1-sheet is covered with helices and loops al, a2a-L5-a2b, a3-L9-a3a on one face, a4-L12-a5 and a6 on the opposite face (Fig. 2G). The overall shape of the core domain is conelike with the exposed N-terminus of / 4 and the loop between /I6 and /17 forming the tip of the cone. In addition to the a/la-sandwich, there are two lobes (Fig. 2D) one lobe of about 30 amino acids at the /12-vertex of the central /1-sheet, consisting of a short helix (ocO) and a small, three-stranded, antiparallel /1-sheet (/lla,b,c), and the second lobe consisting of loop L8 (already mentioned) attached to /14 of the central /1-sheet via the split strand /15. The latter is sometimes called the /15-L8 lobe. Besides loop regions of undefined secondary structure, this lobe contains two /1-strands (/15a and /15b) in antiparallel conformation. 

The monomeric rat kinesin construct (amino acids 1-354) comprises the head domain (including the core motor domain, amino acids 2-325, and the neck linker, amino acids 326-338) and the first half of the neck domain. In the crystal structure, the neck linker consists of two strands, /19 and /110, that form hydrogen bonds with strands / 8 and fJ7 of the core /1-sheet (Fig. 2E). The neck linker ends close to loop L10 at the tip of the core domain where the (a-helical neck domain (helix a7) is attached to the core motor domain. Its orientation is roughly in the plane of the core /1-sheet and perpendicular to the strands. 

Structural elements that interact with the microtubule surface have been identified by the effect of point mutations (Woehlke et al, 1997) and by fitting crystal structures of kinesin motor domains to low-resolution electron density maps obtained by cryo-electron microscopy of microtubules 

Structural Alignment of the Switch-1 and Switch-2 Regions of Kinesin Motor Domains with Secondary Structure Assignments and Classification of the Switch-2 Cluster and Neck/Neck Linker Conformations 

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