5jy7
From Proteopedia
Complex of Mycobacterium smegmatis trehalose synthase with maltokinase
Structural highlights
FunctionTRES_MYCS2 Catalyzes the reversible interconversion of maltose and trehalose by transglucosylation. Maltose is the preferred substrate. To a lesser extent, also displays amylase activity, catalyzing the endohydrolysis of (1->4)-alpha-D-glucosidic linkages in glycogen and maltooligosaccharides such as maltoheptaose, to produce maltose which then can be converted to trehalose. TreS plays a key role in the utilization of trehalose for the production of glycogen, and might also function as a sensor and/or regulator of trehalose levels within the cell. Thus, when trehalose levels in the cell become dangerously low, TreS can expedite the conversion of glycogen to maltose via its amylase activity and then convert the maltose to trehalose; but this enzyme also can expedite or promote the conversion of trehalose to glycogen when cytoplasmic trehalose levels become too high. Is also able to catalyze the hydrolytic cleavage of alpha-aryl glucosides, as well as alpha-glucosyl fluoride in vitro.[1] [2] [3] [4] Publication Abstract from PubMedA growing body of evidence implicates the mycobacterial capsule - the outermost layer of the mycobacterial cell envelope - in modulation of the host immune response and virulence of mycobacteria. Mycobacteria synthesize the dominant capsule component, alpha(1-->4)-linked glucan, via three interconnected, and potentially redundant metabolic pathways. Here, we report the crystal structure of the Mycobacterium smegmatis TreS-Pep2 complex, containing trehalose synthase (TreS) and maltokinase (Pep2), which convert trehalose to maltose-1-phosphate as part of the TreS-Pep2-GlgE pathway. The structure, at 3.6 A resolution, revealed that a diamond-shaped TreS tetramer forms the core of the complex, and that pairs of Pep2 monomers bind to opposite apices of the tetramer in a 4+4 configuration. However, for the M. smegmatis orthologues, results from isothermal titration calorimetry and analytical ultracentrifugation experiments indicated that the prevalent stoichiometry in solution is 4 TreS + 2 Pep2 protomers. The observed discrepancy between the crystallised complex and the behaviour in the solution state may be explained by the relatively weak affinity of Pep2 for TreS (Kd 3.5 muM at mildly acidic pH) and crystal packing favouring the 4+4 complex. Proximity of the ATP binding site in Pep2 to the complex interface provides a rational basis for rate enhancement of Pep2 upon binding to TreS, but the complex structure appears to rule out substrate channeling between the active sites of TreS and Pep2. Our findings provide a structural model for the trehalose synthase-maltokinase complex in M. smegmatis that offers critical insights into capsule assembly. Crystal structure of the TreS-Pep2 complex, initiating alpha-glucan synthesis in the GlgE pathway of mycobacteria.,Kermani AA, Roy R, Gopalasingam C, Kocurek KI, Patel TR, Alderwick LJ, Besra GS, Futterer K J Biol Chem. 2019 Mar 15. pii: RA118.004297. doi: 10.1074/jbc.RA118.004297. PMID:30877199[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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