Table 1.

Nucleotide and amino acid changes introduced to generate syncytin-2 mutants by site-directed mutagenesis.

Mutant site	Residue number	Forward Primer (5′ - 3′)	Allele change	Fusion
1	133	GTGTTATGGCCAAAAGGAAACAGGGAACAAATGTAGGCACTC	aat→cag N→Q	−
2	146	CTCTTCCAAGTACAGTCTGTCAGGTTACTTTCACTGTAGATTC	aat→cag N→Q	+
3	177	CAAGATTCCCCAAACCTCCACAGATTACTTTTCCTCAGGGAAC	aat→cag N→Q	+
4	220	CCAATGTCTGCAAATTTCCCAGCTCAGCTCTACAGCGGAATGG	aac→cag N→Q	+
5	241	CGAAATTCTCTTTTTTGGGAACAGAAAACCAAGGGAGCTAACCAG	aat→cag N→Q	+
6	247	GGAAAATAAAACCAAGGGAGCTCAACAGAGCCAAACACCCTGCGTCC	aac→caa N→Q	+
7	312	CACCAATGCCTCCCCAGTCAATGGACTGGAACTTGTACC	aac→caa N→Q	−
8	332	CTTCATAGCCCCTGGCCAGCTCTCTCTTCCAATAC	aat→cag N→Q	++
9	443	GAAAAATGTTGCTTTTGGGTACAGCAATCAGGAAAAGTACAAGAC	aat→cag N→Q	−
10	523	GGCCATAAAGCTCCAGACGCAACTCAGTGCAGGACGCCATC	aat→caa N→Q	+
11	46	CCACCAATTGCTGGTTACGTACTAGCTCTTCCAC	tgt→cgt N→Q	−
12	118	CCATCTTTACTAATATCAGCCTAATGGGAATAGCCCC	aac→agc N→Q	++
13	359	CATTTCATTCCCCTTCTCACGGGACTCGGCATTCTAG	gcg→acg N→Q	+
14	367	CGGCATTCTAGCTGGTATGGGAACCGGAATTGCTG	acg→atg N→Q	++
15	417	CAGCCGTAGTCCTTCAAAATCATCGAGGACTAGACATGTTAAC	cgt→cat N→Q	−
16	432	GCACAGGGAGGAATTTGTGTGGCCTTAGATGAAAAATG	ttg→gtg N→Q	+
17	483	GGAAATGGTTCTCTTGGATTCTTCCCCTTACAGGC	gtt→att N→Q	++
18	503	GCTCCTTTTTGGTCCATGTTTCCTAAATCTAATAACCC	ctc→ttc N→Q	+
19	518	GTCTCCTCTCGCCTTCAGGCCGTAAAGCTCCAGACGAATCTCA	ata→gta N→Q	+
20	522	GGCCATAAAGCTCCAGATGAATCTCAGTGCAGGAC	acg→atg N→Q	++
21	536	CCTCGCAATATTCAAGAGTTACCCTTCTAGTGACTGCAG	tca→tta N→Q	+

^a Cell fusion was monitored 36 h after transfection. −, no fusion; +, moderate fusion; ++, excessive fusion.