X-Ray Structure and Activities of an Essential Mononegavirales L-Protein Domain.
Paesen, G.C., Collet, A., Sallamand, C., Debart, F., Vasseur, J.J., Canard, B., Decroly, E., Grimes, J.M.(2015) Nat Commun 6: 8749
- PubMed: 26549102 
- DOI: https://doi.org/10.1038/ncomms9749
- Primary Citation of Related Structures:  
4UCI, 4UCJ, 4UCK, 4UCL, 4UCY, 4UCZ, 4UD0 - PubMed Abstract: 
The L protein of mononegaviruses harbours all catalytic activities for genome replication and transcription. It contains six conserved domains (CR-I to -VI; Fig. 1a). CR-III has been linked to polymerase and polyadenylation activity, CR-V to mRNA capping and CR-VI to cap methylation. However, how these activities are choreographed is poorly understood. Here we present the 2.2-Å X-ray structure and activities of CR-VI+, a portion of human Metapneumovirus L consisting of CR-VI and the poorly conserved region at its C terminus, the +domain. The CR-VI domain has a methyltransferase fold, which besides the typical S-adenosylmethionine-binding site ((SAM)P) also contains a novel pocket ((NS)P) that can accommodate a nucleoside. CR-VI lacks an obvious cap-binding site, and the (SAM)P-adjoining site holding the nucleotides undergoing methylation ((SUB)P) is unusually narrow because of the overhanging +domain. CR-VI+ sequentially methylates caps at their 2'O and N7 positions, and also displays nucleotide triphosphatase activity.
Organizational Affiliation: 
Division of Structural Biology, Wellcome Trust Centre for Human Genetics, Oxford OX3 7BN, UK.