1 121140 and 1.23e-02, respectively) strongly suggested that 1cyd (Mus musculus carbonyl
2 reductase complexed with NADPH and 2-propanol) was the closest match to Rv2709 (22%
3 sequence identity). Using the 1cyd co-ordinates and the FUGUE server (Shi et al., 2001) we
4 generated an in silico 3D structure of Rv2509. The predictions revealed similar 3D structural
5 folds for 1cyd, Rv2509 and the E. coli fatty acid reductase, FabG (data not shown).
6 Additionally, when the NADPH moiety from 1cyd was superimposed in the predicted NADP-
7 binding fold of Rv2509, the predicted distances between the conserved residues and the co-
8 factor showed a fit similar to that seen in 1cyd (data not shown). These data suggested that
9 Rv2509 was likely a NAD/NADP-dependent mycobacterial reductase. As outlined above, the
10 homologous M. smegmatis gene MSMEG4722 was chosen for further analysis.
11
12 Deletion of MSMEG4722 in M. smegmatis mc2155 alters culture characteristics and
13 sensitivity to antibiotics
14 To study the role of MSMEG4722 in mycolic acid motif formation, we deleted MSMEG4722 in
15 M. smegmatis mc2155 by specialized transduction (Bardarov et al., 2002) (Figure 2A). The
16 ability to generate a null mutant indicated that MSMEG4722 was not essential for the viability of
17 M. smegmatis mc2155. Loss of MSMEG4722 had a remarkable effect of the colony morphology
18 of M. smegmatis mc2155 on TSB agar. While the colonies of the parental, wild type strain
19 mc2155 were glossy, those of the mutant strain ∆MSMEG4722 appeared to have a dry surface
20 (Figure 2B). The change was more apparent when the strains were grown on TSB agar
21 supplemented with Tween-80. Unlike colonies of the parental strain mc2155 which had a
22 smooth surface, colonies of ∆MSMEG4722 had an irregular, convoluted surface (Figure 2B).