Structural basis for the development of potential inhibitors targeting FadD23 from Mycobacterium tuberculosis.

Sulfolipid‐1 (SL‐1) is a lipid that is abundantly found in the cell wall of Mycobacterium tuberculosis (Mtb). MtbFadD23 is crucial in the SL‐1 synthesis pathway. Previously, 5′‐O‐[N‐(11‐phenoxyundecanoyl)sulfamoyl]adenosine (PhU‐AMS) has been shown to be a general inhibitor of fatty‐acid‐adenylating enzymes (FadDs) in Mtb. However, the fatty acyl‐AMP ligase (FAAL) class of FadDs, which includes MtbFadD23, appears to be functionally nonredundant in the production of multiple fatty acids. In this study, the ability of PhU‐AMS to bind to MtbFadD23 was examined under in vitro conditions. The crystal structure of the MtbFadD23–PhU‐AMS complex was determined at a resolution of 2.64 Å. Novel features were identified by structural analysis and comparison. Although PhU‐AMS could bind to MtbFadD23, it did not inhibit the FAAL adenylation activity of MtbFadD23. However, PhU‐AMS improved the main Tm value in a differential scanning fluorimetry assay, and a structural comparison of MtbFadD23–PhU‐AMS with FadD32 and PA1221 suggested that PhU‐AMS blocks the loading of the acyl chain onto Pks2. This study sheds light on the structure‐based design of specific inhibitors of MtbFadD23 and general inhibitors of FAALs. [ABSTRACT FROM AUTHOR]