A Novel Sugar-stimulated Covalent Switch in a Sugar Sensor

Qing Chen, Anat Nussbaum-Shochat, Orna Amster-Choder

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


The bgl sensory system is composed of a membrane-bound sugar sensor, BGlF, and a transcriptional regulator, BglG. The sensor BglF has several enzymatic activities: in its nonstimulated state, it acts as BglG phosphorylase; in the presence of β-glucoside in the growth medium, it acts as BglG dephosphorylase and as the β-glucoside phosphotransferase. The same active site on BglF, Cys-24, is responsible for the phosphorylation of both the stimulating sugar and the BglG protein. BglF is composed of three domains, two hydrophilic and one hydrophobic. Our previous results suggested that catalysis of the sugar-stimulated functions depends on specific interactions between the B domain, which contains the active site cysteine, and the integral membrane C domain. We report here that the stimulating sugar triggers the formation of a disulfide bond between the active site cysteine and another cysteine in the membrane-embedded domain of BglF. Inability of a mutant BglF protein to form the disulfide bridge between the B and C domains correlates with its inability to catalyze the sugar-stimulated functions. The ability of the cysteine residue in BglF to bind covalently either to a phosphoryl group or to another cysteine residue, depending on the protein stimulation state, suggests a novel way to control signaling by alternative bond formation.

Original languageAmerican English
Pages (from-to)44751-44756
Number of pages6
JournalJournal of Biological Chemistry
Issue number48
StatePublished - 30 Nov 2001


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