TABLE 1.

Primers used in this study

Primer	Sequence (5′ → 3′)a
N-W988A-f	ctgataatctggcaagggcatcaac
N-W988A-b	gttgatgcccttgccagattatcag
N-W1015A-f	gacgggaaaaaagaggcggtcctcgatggttac
N-W1015A-b	gtaaccatcgaggaccgcctcttttttcccgtc
N-W891A-f	catgacagacacccaggcgtcgatgaacggaaactcc
N-W891A-b	gagtttccgttcatcgacgcctgggtgtctgtcatgc
N-W933A-f	cggttcagtcagcagctgtcatgcgtacagacc
N-W933A-b	gtctgtacgcatgacagctgctgactgaaccgc
N-W1015K-f	gacgggaaaaaagagaaagtcctcgatggttacc
N-W1015K-b	gtaaccatcgaggactttctcttttttcccgtcc
N-W1015F-f	gacgggaaaaaagagtttgtcctcgatggttacc
N-W1015F-b	gtaaccatcgaggacaaactcttttttcccgtcc
N-W1015Y-f	gacgggaaaaaagagtatgtcctcgatggttacc
N-W1015Y-b	gtaaccatcgaggacatactcttttttcccgtcc

^a The mutated residues are underlined.