TABLE 2.

Phenotypic characteristics of MTase-like domain mutants

Virus	Virus titer (PFU/ml) at 37°Ca	Proteolytic processing (in vitro)c	nsp2 synthesis in vivo (37°C)	Percentage of RNA synthesise		Minus-strand synthesis at 6 hf
				G	Sg
SINV	1.2 × 109	+	+	100	100	+++
R615A	4.0 × 108b	+	+	5	4.1	++
R699A	−	+	−	4.2	4.9	+
K733A	0.8 × 109	I	I	36.8	24	++
R751A	1.0 × 109	+	+	33.5	71	++
R740A	1.2 × 109	+	+	∼98	∼94	ND
R760A	1.1 × 109	+	+	∼98	∼90	ND
SIN/G	0.94 × 109	NDd	+	ND	ND	ND
SIN/2V	0.82 × 109	ND	I	ND	ND	ND

^aVirus titers were determined by maintaining infected BHK cells under liquid medium at 37°C for 24 h, harvesting the medium, and assaying the production of progeny viruses by standard plaque assay.

^bFor R615A and R699A plaque analysis was performed at 30°C for 48 h. −, no detectable infectious virus released or no detectable protein synthesis.

^cI, polyprotein intermediates observed in addition to full length nsP2.

^dND, not determined.

^ePercent incorporation of inorganic ^[32]P into the genomic (G) and subgenomic (Sg) RNA at 10 h p.i. at 37°C.

^fMinus-strand synthesis levels: +++, 100%; ++, ∼50-100%; +, ∼1-10%.