J. Appl. Cryst.の発刊に際して

The phosphoenolpyruvate(PEP):carbohydrate phosphotransferase system (PTS) is found only in bacteria, where it catalyzes the transport and phosphorylation of numerous monosaccharides, disaccharides, amino sugars, polyols, and other sugar derivatives. To carry out its catalytic function in sugar transport and phosphorylation, the PTS uses PEP as an energy source and phosphoryl donor. The phosphoryl group of PEP is usually transferred via four distinct proteins (domains) to the transported sugar bound to the respective membrane component(s) (EIIC and EIID) of the PTS. The organization of the PTS as a four-step phosphoryl transfer system, in which all P derivatives exhibit similar energy (phosphorylation occurs at histidyl or cysteyl residues), is surprising, as a single protein (or domain) coupling energy transfer and sugar phosphorylation would be sufficient for PTS function. A possible explanation for the complexity of the PTS was provided by the discovery that the PTS also carries out numerous regulatory functions. Depending on their phosphorylation state, the four proteins (domains) forming the PTS phosphorylation cascade (EI, HPr, EIIA, and EIIB) can phosphorylate or interact with numerous non-PTS proteins and thereby regulate their activity. In addition, in certain bacteria, one of the PTS components (HPr) is phosphorylated by ATP at a seryl residue, which increases the complexity of PTS-mediated regulation. In this review, we try to summarize the known protein phosphorylation-related regulatory functions of the PTS. As we shall see, the PTS regulation network not only controls carbohydrate uptake and metabolism but also interferes with the utilization of nitrogen and phosphorus and the virulence of certain pathogens.

How Phosphotransferase System-Related Protein Phosphorylation Regulates Carbohydrate Metabolism in Bacteria

https://www.cell.com/molecular-cell/pdf/S1097-2765(03)00313-7.pdf

A tweezers-like motion of the ATP-binding cassette dimer in an ABC transport cycle.

STAND, a class of P-loop NTPases including animal and plant regulators of programmed cell death: multiple, complex domain architectures, unusual phyletic patterns, and evolution by horizontal gene transfer.

The processes responsible for the evolution of key innovations, whereby lineages acquire qualitatively new functions that expand their ecological opportunities, remain poorly understood. We examined how a virus, bacteriophage λ, evolved to infect its host, Escherichia coli, through a novel pathway. Natural selection promoted the fixation of mutations in the virus’s host-recognition protein, J, that improved fitness on the original receptor, LamB, and set the stage for other mutations that allowed infection through a new receptor, OmpF. These viral mutations arose after the host evolved reduced expression of LamB, whereas certain other host mutations prevented the phage from evolving the new function. This study shows the complex interplay between genomic processes and ecological conditions that favor the emergence of evolutionary innovations.

/pdf/repeatability-and-contingency-in-the-evolution-of-a-key-13qas4m2tp.pdf

Repeatability and Contingency in the Evolution of a Key Innovation in Phage Lambda

https://kops.uni-konstanz.de/bitstream/handle/123456789/8677/Structural_model_of_MalK.pdf;sequence=1

Structural model of MalK, the ABC subunit of the maltose transporter of Escherichia coli: Implications for mal gene regulation, inducer exclusion, and subunit assembly

Learning new tricks from an old dog: MalT of the Escherichia coli maltose system is part of a complex regulatory network

Gene regulation in prokaryotes by subcellular relocalization of transcription factors.

MalK, the ATP-binding Cassette Component of the Escherichia coli Maltodextrin Transporter, Inhibits the Transcriptional Activator MalT by Antagonizing Inducer Binding

The genes of the Escherichia coli maltose regulon are controlled by MalT, the specific transcriptional activator which, together with the inducer maltotriose and ATP, is essential for mal gene transcription. Network regulation in this system affects the function of MalT and occurs on two levels. The first concerns the expression of malT .I t has long been known that malT is under catabolite repression and thus under the control of the cAMP/CAP complex. We found that, in addition, the global regulator Mlc is a repressor for malT transcription. The repressor activity of Mlc is controlled by the transport status of the glucose-specific enzyme EIICB of the PTS that causes sequestration (and inactivation as a repressor) of Mlc when glucose is transported. The second level of MalT regulation affects its activity. MalT is activated by maltotriose which is not only formed when the cells are growing on any maltodextrin but also, in low amounts, endogenously when the cells grow on non-maltodextrin carbon sources. Thus, cellular metabolism, for instance degradation of galactose or trehalose, can cause mal gene induction. It was found that unphosphorylated internal glucose takes part in endogenous maltodextrin biosynthesis and is therefore a key element in endogenous mal gene expression. In addition to the maltotriose-dependent activation, MalT can interact with three different enzymes that lead to its inactivation as a transcriptional activator. The first is MalK, the energy transducing ABC subunit of the maltodextrin transport system. Transport controls the interaction of MalK and MalT thus affecting gene expression. The second enzyme is MalY, a pyridoxal phosphate containing enzyme exhibiting cystathionase activity. The crystal structure of MalY was established and mutations in MalY that reduce mal gene repression map in a hydrophobic MalT interaction patch on the surface of the enzyme. The last enzyme is a soluble esterase of as yet unknown function. When overproduced, this enzyme specifically reduces mal gene expression and affects the activity of MalT in an in vitro transcription assay.

/pdf/network-regulation-of-the-escherichia-coli-maltose-system-4vt6kobi3x.pdf

Alex Böhm

Papers

Structural model of MalK, the ABC subunit of the maltose transporter of Escherichia coli: Implications for mal gene regulation, inducer exclusion, and subunit assembly

Learning new tricks from an old dog: MalT of the Escherichia coli maltose system is part of a complex regulatory network

Gene regulation in prokaryotes by subcellular relocalization of transcription factors.

MalK, the ATP-binding Cassette Component of the Escherichia coli Maltodextrin Transporter, Inhibits the Transcriptional Activator MalT by Antagonizing Inducer Binding

Network regulation of the Escherichia coli maltose system.