Transcription of malP is subject to phosphotransferase system-dependent regulation in Corynebacterium glutamicum.

Abstract

The Gram-positive Corynebacterium glutamicum co-metabolizes most carbon sources such as the phosphotransferase system (PTS) sugar glucose and the non-PTS sugar maltose. Maltose is taken up via the ABC-transporter MusEFGK2I, and is further metabolized to glucose phosphate by amylomaltase MalQ, maltodextrin phosphorylase MalP, glucokinase Glk and phosophoglucomutase Pgm. Surprisingly, growth of C. glutamicum strains lacking the general PTS components EI or HPr was strongly impaired on the non-PTS sugar maltose. Complementation experiments showed that a functional PTS phosphorelay is required for optimal growth of C. glutamicum on maltose, implying its involvement in the control of maltose metabolism and/or uptake. To identify the target of this PTS-dependent control, transport measurements with 14C-labelled maltose, Northern blot analyses and enzyme assays were performed. The activities of the maltose transporter and enzymes MalQ, Pgm and GlK were not decreased in PTS-deficient C. glutamicum strains, which was corroborated by comparable transcript amounts of musE, musK and musG, as well as of malQ, in C. glutamicum ΔptsH and WT. By contrast, MalP activity was significantly reduced and only residual amounts of malP transcripts were detected in C. glutamicum ΔptsH when compared to WT. Promoter activity assays with the malP promoter in C. glutamicum ΔptsH and WT confirmed that malP transcription is reduced in the PTS-deficient strain. Taken together, we show here for what is to the best of our knowledge the first time a regulatory function of the PTS in C. glutamicum and identify malP transcription as its target.