Dissecting the Ca2+ dependence of DesA1 function in Mycobacterium  tuberculosis

The desaturase DesA1 is an essential protein involved in the biosynthesis of mycolic acids, a class of lipids crucial to the structural maintenance of theMycobacterium tuberculosis cell wall. We demonstrate here that Ca2+-binding is critical to DesA1 function – disrupting this binding by mutating the Ca2+-binding site, leads to a defect in growth and compromises bacillary cell wall integrity. Mycobacterium  tuberculosis (M.  tb) has a complex cell wall, composed largely of mycolic acids, that are crucial to its structural maintenance. TheM.  tb desaturase A1 (DesA1) is an essential Ca2+-binding protein that catalyses a key step in mycolic acid biosynthesis. To investigate the structural and functional significance of Ca2+ binding, we introduced mutations at key residues in its Ca2+-binding βγ-crystallin motif to generate DesA1F303A, E304Q, and F303A-E304Q. Complementation of a conditional ΔdesA1 strain ofMycobacterium smegmatis, with the Ca2+ non-binders F303A or F303A-E304Q, failed to rescue its growth phenotype; these complements also exhibited enhanced cell wall permeability. Our findings highlight the criticality of Ca2+ in DesA1 function, and its implicit role in the maintenance of mycobacterial cellular integrity.
Source: FEBS Letters - Category: Biochemistry Authors: Tags: Research Letter Source Type: research