Sinorhizobium meliloti low molecular weight phosphotyrosine phosphatase SMc02309 modifies activity of the UDP-glucose pyrophosphorylase ExoN involved in succinoglycan biosynthesis
Medeot DB, Rivero MR, Cendoya E, Contreras-Moreira B, Rossi FA, Fischer SE, Becker A, Jofré E (2016) Sinorhizobium meliloti low molecular weight phosphotyrosine phosphatase SMc02309 modifies activity of the UDP-glucose pyrophosphorylase ExoN involved in succinoglycan biosynthesis, Microbiology, doi: 10.1099/mic.0.000239.
In Gram-negative bacteria, tyrosine phosphorylation has been shown to play a role in the control of exopolysaccharide (EPS) production. This report demonstrates that the chromosomal open reading frame SMc02309 from Sinorhizobium meliloti 2011, encodes a protein with significant sequence similarity to low molecular weight protein tyrosine phosphatases (LMW-PTPs), such as the Escherichia coli Wzb. Unlike other well-characterized EPS biosynthesis gene clusters, which contain neighboring LMW-PTPs and kinase, the S. meliloti succinoglycan (EPS I) gene cluster located on megaplasmid pSymB does not encode a phosphatase. Biochemical assays revealed that the SMc02309 protein hydrolyzes p-nitrophenyl phosphate (p-NPP) with kinetic parameters similar to other bacterial LMW-PTPs. Furthermore, we show evidence that SMc02309 is not the LMW-PTP of the bacterial tyrosine-kinase (BY-kinase) ExoP. Nevertheless ExoN, a UDP-glucose pyrophosphorylase involved in the first stages of EPS I biosynthesis, is phosphorylated at tyrosine residues and constitutes an endogenous substrate of the SMc02309 protein. Additionally, we show that the UDP-glucose pyrophosphorylase activity is modulated by SMc02309-mediated tyrosine dephosphorylation. Moreover, a mutation in the SMc02309 gene decreases EPS I production and delays nodulation on M. sativa roots.
In Gram-negative bacteria, tyrosine phosphorylation has been shown to play a role in the control of exopolysaccharide (EPS) production. This report demonstrates that the chromosomal open reading frame SMc02309 from Sinorhizobium meliloti 2011, encodes a protein with significant sequence similarity to low molecular weight protein tyrosine phosphatases (LMW-PTPs), such as the Escherichia coli Wzb. Unlike other well-characterized EPS biosynthesis gene clusters, which contain neighboring LMW-PTPs and kinase, the S. meliloti succinoglycan (EPS I) gene cluster located on megaplasmid pSymB does not encode a phosphatase. Biochemical assays revealed that the SMc02309 protein hydrolyzes p-nitrophenyl phosphate (p-NPP) with kinetic parameters similar to other bacterial LMW-PTPs. Furthermore, we show evidence that SMc02309 is not the LMW-PTP of the bacterial tyrosine-kinase (BY-kinase) ExoP. Nevertheless ExoN, a UDP-glucose pyrophosphorylase involved in the first stages of EPS I biosynthesis, is phosphorylated at tyrosine residues and constitutes an endogenous substrate of the SMc02309 protein. Additionally, we show that the UDP-glucose pyrophosphorylase activity is modulated by SMc02309-mediated tyrosine dephosphorylation. Moreover, a mutation in the SMc02309 gene decreases EPS I production and delays nodulation on M. sativa roots.