4ud4

Publication Abstract from PubMed

Terminal uridylyl transferases (TUTs) are responsible for the post-transcriptional addition of uridyl residues to RNA 3' ends, leading in some cases to altered stability. The Schizosaccharomyces pombe TUT Cid1 is a model enzyme that has been characterized structurally at moderate resolution and provides insights into the larger and more complex mammalian TUTs, ZCCHC6 and ZCCHC11. Here, we report a higher resolution (1.74 A) crystal structure of Cid1 that provides detailed evidence for uracil selection via the dynamic flipping of a single histidine residue. We also describe a novel closed conformation of the enzyme that may represent an intermediate stage in a proposed product ejection mechanism. The structural insights gained, combined with normal mode analysis and biochemical studies, demonstrate that the plasticity of Cid1, particularly about a hinge region (N164-N165), is essential for catalytic activity, and provide an explanation for its distributive uridylyl transferase activity. We propose a model clarifying observed differences between the in vitro apparently processive activity and in vivo distributive monouridylylation activity of Cid1. We suggest that modulating the flexibility of such enzymes-for example by the binding of protein co-factors-may allow them alternatively to add single or multiple uridyl residues to the 3' termini of RNA molecules.

Structural plasticity of Cid1 provides a basis for its distributive RNA terminal uridylyl transferase activity.,Yates LA, Durrant BP, Fleurdepine S, Harlos K, Norbury CJ, Gilbert RJ Nucleic Acids Res. 2015 Mar 11;43(5):2968-79. doi: 10.1093/nar/gkv122. Epub 2015 , Feb 20. PMID:25712096^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.