LipoproteinN-acyl transferase (Lnt1) is dispensable for proteinO-mannosylation byStreptomyces coelicolor

Abstract

A protein glycosylation system related to that for protein mannosylation in yeast is present in many actinomycetes. This system involves polyprenyl phosphate mannose synthase (Ppm), protein mannosyl transferase (Pmt), and lipoprotein N-acyl transferase (Lnt). In this study, we obtained a series of mutants in the ppm (sco1423), lnt1 (sco1014), and pmt (sco3154) genes of Streptomyces coelicolor, which encode Ppm, Lnt1, and Pmt, to analyze their requirement for glycosylation of the heterologously expressed Apa glycoprotein of Mycobacterium tuberculosis. The results show that both Ppm and Pmt were required for Apa glycosylation, but that Lnt1 was dispensable for both Apa and the bacteriophage φC31 receptor glycosylation. A bacterial two-hybrid assay revealed that contrary to M.tuberculosis, Lnt1 of S.coelicolor does not interact with Ppm. The D2 catalytic domain of M.tuberculosisPpm was sufficient for complementation of an S.coelicolor double mutant lacking Lnt1 and Ppm, both for Apa glycosylation and for glycosylation of φC31 receptor. On the other hand, M.tuberculosisPmt was not active in S.coelicolor, even when correctly localized to the cytoplasmic membrane, showing fundamental differences in the requirements for Pmt activity in these two species.