Isoprenoid chain elongation in Mycobacterium tuberculosis

Abstract

Isoprenyl diphosphate synthases catalyze the sequential addition of isopentenyl diphosphate to an allylic diphosphate acceptor until a physiologically relevant chain length has been reached. Seven open reading frames from the Mycobacterium tuberculosis H37Rv genome were identified as putative isoprenyl diphosphate synthases based on amino acid sequence similarities to known isoprenyl diphosphate synthases. In an attempt to map the pathway for the synthesis of decaprenyl phosphate, these open reading frames were cloned and overexpressed in M. smegmatis. Protein derived from wildtype or recombinant M. smegmatis was assayed for isoprenyl diphosphate synthase activity. This strategy yielded the identification of two unique Z-isoprenyl diphosphate synthases (corresponding to open reading frames Rv1086 and Rv2361c) and one E-isoprenyl diphosphate synthase (corresponding to open reading frame Rv3398c). tested for Rv1086 was further purified to homogeneity and activity in the presence of inhibitors.