294d
From Proteopedia
INTERCALATED CYTOSINE MOTIF AND NOVEL ADENINE CLUSTERS IN THE CRYSTAL STRUCTURE OF TETRAHYMENA TELOMERE
Overview
The cytosine-rich strand of the Tetrahymena telomere consists of multiple repeats of sequence d(AACCCC). We have solved the crystal structure of the crystalline repeat sequence at 2.5 A resolution. The adenines form two different and previously unknown clusters (A clusters) in orthogonal directions with their counterparts from other strands, each containing a total of eight adenines. The clusters appear to be stable aggregates held together by base stacking and three different base-pairing modes. Two different types of cytosine tetraplexes are found in the crystal. Each four-stranded complex is composed of two intercalated parallel-stranded duplexes pointing in opposite directions, with hemiprotonated cytosine-cytosine (C.C+) base pairs. The outermost C.C+base pairs are from the 5'-end of each strand in one cytosine tetraplex and from the 3'-end of each strand in the other. The A clusters and the cytosine tetraplexes form two alternating stacking patterns, creating continuous base stacking in two perpendicular directions along the x - and z -axes. The adenine clusters could be organizational motifs for macromolecular RNA.
About this Structure
Full crystallographic information is available from OCA.
Reference
Intercalated cytosine motif and novel adenine clusters in the crystal structure of the Tetrahymena telomere., Cai L, Chen L, Raghavan S, Ratliff R, Moyzis R, Rich A, Nucleic Acids Res. 1998 Oct 15;26(20):4696-705. PMID:9753739 Page seeded by OCA on Sat May 3 18:26:02 2008
