View larger version (32K):
[in a new window]
|
Fig. 4. Domain organization of kinesin I and KIF1A. For kinesin I, its heavy and
light polypeptide chains are shown in red and green, respectively. Amino-acid
residues in parentheses are referenced to the mouse ubiquitous isoform.
Cargo-binding domains (CBD) are indicated by black on white labels; domains
involved in regulation of motor activity are indicated by black on white
labels. KIF1A, like other KIF1 kinesins, have much shorter coiled-coil regions
than kinesin I, and these promote dimerization of KIF1 polypeptides that are
brought into close proximity on the cargo surface
(Klopfenstein et al., 2002 ;
Tomishige et al., 2002). Thus,
KIF1 polypeptides are monomers in the cytosol
(Nangaku et al., 1994;
Okada et al., 1995), and
through dimerization, presumably on the cargo surface, acquire the ability to
walk along microtubules processively, like native kinesin I does
(Tomishige et al., 2002). It
is appealing to consider that dimerization regulates motor activity of KIF1
kinesins like folding regulates kinesin I activity (see text). The function of
the FHA domain, which marks all KIF1 family members, is unknown, but may be
involved in regulating dimerization. Liprin and MAGUK cargo-binding domains
(LBD and MBS) overlap. The pleckstrin homology domain (PH) is probably a
separate cargo-binding domain
(Klopfenstein et al., 2002).
The amino-acid residues in parentheses are referenced to the mouse isoform of
KIF1A.
|
