In addition, the optically active and the optically inactive (racemic) forms of the compound were synthesized, and the ability of the solute to act as a protecting agent against heating was tested on several proteins derived from mesophilic or hyperthermophilic sources. This solute was purified after extraction from the cell biomass.
#Cyme tcc Activator#
Therefore, we propose that a direct protein–protein interaction with MalT, the central transcriptional activator of the maltose system, underlies MalY-dependent repression of the maltose system.ĭiglycerol phosphate accumulates under salt stress in the archaeon Archaeoglobus fulgidus (L. The tertiary structure of one of these mutants (A221V) demonstrates that positional rearrangements are indeed restricted to regions I, II and III. In a screen for MalY mutants with reduced mal repressor properties, mutations occurred in three clusters: I, 83–84 II, 181–189 and III, 215–221, which constitute a clearly distinguished region in the MalY crystal structure far away from the cofactor. The structural alignment with related enzymes identifies residues that are generally responsible for β–lyase activity and depicts a unique binding mode of the pyridoxal 5′–phosphate correlated with a larger, more flexible substrate-binding pocket. Each subunit of the MalY dimer is composed of a large pyridoxal 5′-phosphate-binding domain and a small domain similar to aminotransferases. Here we present the crystal structures of wild-type and A221V mutant protein. MalY represents a bifunctional pyridoxal 5′-phosphate-dependent enzyme acting as a β–cystathionase and as a repressor of the maltose regulon. Strains which gained this capacity by mutation could easily be selected, however. coli mal mutants on linear maltodextrin was not observed when the cells harbored only the cym uptake system. oxytoca cym system, but because of the inability of maltodextrins to induce the cym system, growth of E. Besides α-cyclodextrin, maltohexaose was also taken up by the K. oxytoca three to five times less efficiently than maltohexaose by the E. In transport experiments, α-cyclodextrin was taken up by the cym system of K. CymE bound α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin, with dissociation constants (Kd) of 0.02, 0.14 and 0.30 μM, respectively, and linear maltoheptaose, with a Kd of 70 μM. By substrate-induced fluorescence quenching, the binding of ligands was analyzed. CymE, which is the periplasmic binding protein, has been overproduced and purified. Cyclodextrin transport is mediated by the products of the cymE, cymF, cymG, cymD, and cymA genes, which are functionally homologous to the malE, malF, malG, malK, and lamB gene products of Escherichia coli. Klebsiella oxytoca M5a1 has the capacity to transport and to metabolize α-, β- and γ-cyclodextrins. The gene encoding MalP was obtained by complementation in Escherichia coli and sequenced (calculated molecular mass. litoralis were purified to homogeneity and characterized they were constitutively synthesized, although phosphorylase expression was twofold induced by maltodextrins or maltose. The two key enzymes in the pathway for maltose catabolism in T. litoralis, but maltose was not a substrate for this enzyme. A PNPG-hydrolyzing activity was also detected in T. The closely related organism Pyrococcus furiosus used a different metabolic strategy in which maltose was cleaved primarily by the action of an α-glucosidase, a p-nitrophenyl-α-d-glucopyranoside (PNPG)-hydrolyzing enzyme, producing glucose from maltose. Glucose derived from the action of 4-α-glucanotransferase was subsequently metabolized via an Embden-Meyerhof pathway. Phosphoglucomutase activity was also detected in T.
#Cyme tcc series#
The first enzyme produced glucose and a series of maltodextrins that could be acted upon by MalP when the chain length of glucose residues was equal or higher than four, to produce glucose-1-phosphate. Maltose was degraded by the concerted action of 4-α-glucanotransferase and maltodextrin phosphorylase (MalP). Maltose metabolism was investigated in the hyperthermophilic archaeon Thermococcus litoralis.