TABLE 3.

Comparison of A domain specificity codes from CMN and VIO NRPSs

CMN or VIO NRPS componenta	Specificity codeb	Amino acid proposed to be activatedc
CmnF	D A Q S L A V V	l-2,3-DAP
VioF	D A Q S L A I V	l-2,3-DAP
CmnA, A1	D V Y H F S L V	l-Ser (or l-Ala)
VioA, A1	D V Y H F S L V	l-Ser
CmnA, A2	D V R S L S M V	l-2,3-DAP
VioA, A2	D V R H M S M V	l-Ser
CmnG	D P Q D I G I V	CAM
VioG	D P Q D V G I G	CAM
CmnO	D T E D V G T M	β-Lys
VioO	D T E D V G V G	β-Lys

^aNRPS components are grouped according to homology (e.g., VioF is the homolog of CmnF). CmnA and VioA each contain more than one A domain. The first A domain is noted as A1, and the second is noted as A2.

^bSpecificity code as described in references 6 and 30. The alignment program to identify the substrate specificity code is available at http://www.tigr.org/jravel/nrps.

^cThis proposal is based on the results of the A domain substrate specificity code and the chemical structures of CMN and VIO. CAM, 2S,3R-capreomycidine.