|
Figure 1.
Figure 1 Ribbon diagram of the structures of Mlc1p bound to IQ2
and IQ4 of Myo2p. (A) Compact structure of the Mlc1p -IQ2
complex. The N-lobe, the C-lobe and the IQ peptide are shown in
blue, red and green, respectively (this color scheme is kept
through all the figures). (B) Extended structure of the Mlc1p
-IQ4 complex. (C) Superimposition of the structures of Mlc1p
-IQ2 and Mlc1p -IQ4 (thinner trace). (D) Superimposition of the
structures of Mlc1p -IQ2 with those of ELC -IQ complexes from
scallop (yellow) and smooth muscle (pink) myosins (Xie et al.,
1994; Houdusse and Cohen, 1996; Dominguez et al., 1998). Note
how differences in the orientation of the N-lobes are mirrored
by differences in the orientation of the C-terminal portions of
the IQ motifs. (E) Superimposition of the extended structures of
Mlc1p -IQ4 and scallop RLC -IQ (cyan) complexes. The myosin
heavy chain fragment (yellow) bound to the scallop RLC is bent
by  90°.
The Mg2+-bound (and fully open) N-lobe of the RLC binds to a
conserved sequence (WQWWKLYSKVKPLL) of the myosin heavy chain
that follows immediately after the 90° turn. Note that this
N-lobe-specific target sequence does not make up part of a
canonical IQ motif.
|
