2c51: Difference between revisions

[[Image:2c51.gif|left|200px]]<br /><applet load="2c51" size="350" color="white" frame="true" align="right" spinBox="true"  

We have determined the X-ray structures of six MS2 RNA hairpin-coat-protein complexes having five different substitutions at the hairpin loop base -5. This is a uracil in the wild-type hairpin and contacts the coat protein both by stacking on to a tyrosine side chain and by hydrogen bonding to an asparagine side chain. The RNA consensus sequence derived from coat protein binding studies with natural sequence variants suggested that the -5 base needs to be a pyrimidine for strong binding. The five -5 substituents used in this study were 5-bromouracil, pyrimidin-2-one, 2-thiouracil, adenine, and guanine. The structure of the 5-bromouracil complex was determined to 2.2 A resolution, which is the highest to date for any MS2 RNA-protein complex. All the complexes presented here show very similar conformations, despite variation in affinity in solution. The results suggest that the stacking of the -5 base on to the tyrosine side chain is the most important driving force for complex formation. A number of hydrogen bonds that are present in the wild-type complex are not crucial for binding, as they are missing in one or more of the complexes. The results also reveal the flexibility of this RNA-protein interface, with respect to functional group variation, and may be generally applicable to other RNA-protein complexes.

2C51 is a [http://en.wikipedia.org/wiki/Protein_complex Protein complex] structure of sequences from [http://en.wikipedia.org/wiki/Enterobacterio_phage_ms2 Enterobacterio phage ms2]. This structure supersedes the now removed PDB entry 1H8J. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2C51 OCA].  

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