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Figure 1.
Fig. 1. Two sections of electron density at 1.0-Å
resolution. (A) Segment of four glucoses, G25 to G2, showing one
of the two bandflip sites in CA26 defined by G26-G1; these two
glucoses are stabilized in anti orientation by the three-center
hydrogen bond
O(3)[26]---H···(O(5)[1],O(6)[1]. The
adjacent glucoses on both sides of the flip are oriented syn as
usually found in amylose chains and hydrogen bonded
O(3)[n]···O(2)[n+1]. Because the flip at
G26-G1 involves not just a single glucose but the whole appended
amylose chain, it was called "band-flip" (18). Labels of O(2)
and O(3) hydroxyl groups are circled to emphasize the abrupt
structural change at the band-flip site. (B) Disordered water
molecules located in the channel-like cavity of the V-amylose
helix. Because the distances between their positions (marked *)
are shorter than the minimum hydrogen bonding distance of 2.5
Å (30), the occupations are around 0.5. Drawn with O (31).
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