id	author	title	date	pages	extension	mime	words	sentences	flesch	summary	cache	txt
cord-271701-tx0lqgff	te Velthuis, Aartjan J.W.	The SARS-coronavirus nsp7+nsp8 complex is a unique multimeric RNA polymerase capable of both de novo initiation and primer extension	2011-10-29		.txt	text/plain	7357	367	56	Commonly, its core subunit is a single RNA-dependent RNA polymerase (RdRp) that drives the production of template strands for replication, new genome molecules, and-in many RNA virus groupsalso subgenomic (sg) mRNAs. This canonical RdRp is structurally conserved among RNA viruses and widely accepted to drive catalysis of phosphodiester bond formation via a well-established reaction mechanism involving two metal ions that are coordinated by aspartate residues in its motifs A and C (3) (4) (5) . Interestingly, both nsp8 and nsp(7+8) are able to extend the RNA primers beyond template length in the presence of heparin ( Figure 4D and Supplementary Figure S2B ), suggesting that these extensions result from terminal transferase activity and not from template switching, as was previously observed for poliovirus 3D pol (20) . Subsequent alanine substitution of the N-terminal D/ ExD/E motif, composed of D50 and D52 in SARS-CoV, greatly affected primer extension activity on the CU 10 template as shown in Figure 5C .	./cache/cord-271701-tx0lqgff.txt	./txt/cord-271701-tx0lqgff.txt