Biology Reference
In-Depth Information
property of annexin V self-organization has been proposed to be functionally
relevant in its biological function. 29 The structure of its soluble form has
been solved by X-ray crystallography and that of the membrane-bound form
was investigated extensively by electron crystallography and AFM. 30 The
fundamental oligomeric state of annexin V is a trimer and trimers assemble
into two common crystal forms with p3 or p6 symmetry. In this section, we
briely demonstrate some dynamic events, such as crystal growth, dynamic
equilibrium between the 2D crystal and the liquid phase, observed in annexin
V crystals with p6 symmetry.
As lipids, we here used DOPC, DOPS and DOPE (5 : 2 : 3 w/w). The lipid
bilayer supported on a mica surface was prepared by the same method
described in section 8.3.1. Two-dimensional crystallization of annexin V on
the bilayer was performed by injecting an annexinV solution into the bilayer
sample during AFM imaging. The buffer used for the observation was 50 mM
Tris-HCl pH 8.0, 5 mM KCl, 2.5 mM MgCl 2 , 3 mM CaCl 2 .
Figure 8.7. Binding and dissociation dynamics of annexin V trimers on the 2D crystal
with p6 symmetry. For example, the hole in the honeycomb lattice indicated by an
arrow in the 0-second image is illed by a trimer diffusing on the crystal surface at 0.5
seconds and then dissociate in the next 0.5 seconds. Successive images were obtained
at an imaging rate of 0.5 s/frame with a scan area of 150
s
150 nm 2 .
The annexin V crystal with p6 symmetry exhibits a honeycomb
structure. The “holes” of the honeycomb structure tend to be occupied with
a relatively mobile trimer, which undergoes a more relaxed interaction
with its surrounding cage than a molecule forming part of the honeycomb
lattice. Because of this mobility, the central trimer, therefore, shows a less
sharply deined density in the EM images of the crystal.
Figure 8.7 shows
successive AFM images obtained at an imaging rate of 0.5 s/frame. The
31,32
 
 
 
Search WWH ::




Custom Search