Structure of an RNA dodecamer containing a fragment from SRP domain IV of Escherichia coli

• Published in: Acta crystallographica. Section D, Biological crystallography. Vol. 59; no. 6; pp. 1004 - 1011
• Main Authors: Deng, Junpeng, Xiong, Yong, Pan, Baocheng, Sundaralingam, Muttaiya
• Format: Journal Article
• Language: English
• Published: 5 Abbey Square, Chester, Cheshire CH1 2HU, England Munksgaard International Publishers 01.06.2003
• Subjects: Crystallization; Escherichia coli - chemistry; hydrated metal-ion binding; Hydrogen Bonding; internal loop; Metals - chemistry; Models, Molecular; Nucleic Acid Conformation; Protein Conformation; RNA crystal packing; RNA, Bacterial - chemistry; RNA-protein interactions; Signal Recognition Particle - chemistry; Water - chemistry
• DOI: 10.1107/S0907444903006747
• ISSN: 1399-0047; 0907-4449

The crystal structure of an RNA dodecamer, r(GCGUCAGGUCBrCG)/r(CGGAAGCAGBrCGC), containing a fragment from the signal recognition particle (SRP) RNA (domain IV) of Escherichia coli, has been determined at 1.7 Å resolution with 21 666 independent reflections and an Rwork and Rfree of 20.1 and 22.5%, respectively. The structure exhibits a novel crystal packing pattern for RNA oligomer duplexes: one end of the duplex adopts the stacking interaction, while the other end adopts the abutting interaction in the minor groove. The symmetric loop of the SRP, r(CAGG)/r(AGCA), in the center of the dodecamer forms two different conformations of the A·C mismatch, a sheared G·G and a symmetrical G·A mismatch. These four mismatches present a unique surface for the abutting interaction. The involvement of the two A·C mismatches in the abutting interaction implies that these mismatches are the important sites for interaction with proteins. The conformation of the symmetric loop is greatly stabilized by hydrated metal ions, which display flexibility in adjusting their geometry and coordination in interaction with nucleic acids. Comparison with other crystal structures of fragments of 4.5S RNA indicates that the conformation of the symmetric loop is independent of the asymmetrical loop in domain IV.