Table 2.

Specificity-conferring amino acids and homologies of the adenylation domains in polymyxin synthetases of strains M-1, E681, and PKB1

Module/ strain	Active site residues in A-domain								Specified aa	% aa E681	% aa PKB1
	235	236	239	278	299	301	322	330
Module 1
pmxE1/M-1	D	V	G	E	I	S	S	I	L-Dab	99	99
pmxE1/E681	D	V	G	E	I	S	S	I	L-Dab
pmxE1/PKB1	D	V	W	E	I	S	S	I	L-Dab
Module 2
pmxE2/M-1	D	F	W	N	I	G	M	V	L-Thr	99	98
pmxE2/E681	D	F	W	N	I	G	M	V	L-Thr
pmxE2/PKB1	D	F	W	N	I	G	M	V	L-Thr
Module 3 (W)
pmxE3/M-1	D	V	G	E	I	S	S	I	D-Dab	98	92
pmxE3/E681	D	V	G	E	I	S	S	I	D-Dab
pmxE3/PKB1	D	V	G	E	I	S	S	I	D-Dab
Module 4
pmxE4/M-1	D	V	G	E	I	S	A	I	L-Dab	96	96
pmxE4/E681	D	V	G	E	I	S	A	I	L-Dab
pmxE4/PKB1	D	V	G	E	I	S	A	I	L-Dab
Module 5
pmxE1/M-1	D	V	G	E	I	S	A	I	L-Dab	97	89
pmxE1/E681	D	V	G	E	I	S	A	I	L-Dab
pmxE1/PKB1	D	V	G	E	I	S	A	I	L-Dab
Module 6 (X)
pmxA1/M-1	D	A	W	T	I	A	A	I	D-Phe	88	99
pmxA1/E681	D	A	W	I	V	G	A	I	D-Leu
pmxA1/PKB1	D	A	W	T	I	A	A	I	D-Phe
Module 7 (Y)
pmxA2/M-1	D	F	W	N	I	G	M	V	L-Thr	99	51
pmxA2/E681	D	F	W	N	I	G	M	V	L-Thr
pmxA2/PKB1	D	G	F	L	L	G	L	V	L-Leu
Module 8
pmxA3/M-1	D	V	G	E	I	S	A	I	L-Dab	97	92
pmxA3/E681	D	V	G	E	I	S	A	I	L-Dab
pmxA3/PKB1	D	V	G	E	I	S	A	I	L-Dab
Module 9
pmxA4/M-1	D	V	G	E	I	S	A	I	L-Dab	96	91
pmxA4/E681	D	V	G	E	I	S	A	I	L-Dab
pmxA4/PKB1	D	V	G	E	I	S	A	I	L-Dab
Module 10 (Z)
pmxB1/M-1	D	F	W	N	I	G	M	V	L-Thr	97	99
pmxB1/E681	D	F	W	N	I	G	M	V	L-Thr
pmxB1/PKB1	D	F	W	N	I	G	M	V	L-Thr

Modules 3 and 6 contained extra epimerization domains which might convert Dab3 and Phe6 to the D-configuration. A-domains in modules 6 (X) and 7(Y) specifying different amino acids in the polymyxins produced by M-1, E681, and PKB1 are underlined.