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Results 1 - 8 of 8
EC Number
General Information
Commentary
Reference
malfunction
construction of a chromosomal wbdDO9a::aacC1 mutation by allelic exchange. Membranes of the mutant are still able to synthesize O9a polymannan in vitro, although the chain length is increased relative to that made by the parent
malfunction
construction of a chromosomal wbdDO9a::aacC1 mutation by allelic exchange. Membranes of the mutant are still able to synthesize O9a polymannan in vitro, although the chain length is increased relative to that made by the parent; membrane preparations from a wbdD mutant have severely diminished mannosyltransferase activity in vitro, and no significant amounts of the WbdA protein are targeted to the membrane fraction. Expression of a polypeptide comprising the WbdD C-terminal region is sufficient to restore both proper localization of WbdA and mannosyltransferase activity
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malfunction
membrane preparations from a wbdD mutant have severely diminished mannosyltransferase activity in vitro, and no significant amounts of the WbdA protein are targeted to the membrane fraction. Expression of a polypeptide comprising the WbdD C-terminal region is sufficient to restore both proper localization of WbdA and mannosyltransferase activity
physiological function
In Escherichia coli O9a, the peripheral membrane protein WbdD terminates polymerization by adding a methyl phosphate to the non-reducing end of the nascent O9a polymer. The O9a system is a representative of the widespread ATP-binding cassette transporter-dependent assembly pathway. This terminal modification is required for recognition and export of the completed O-PS across the cytoplasmic membrane by its cognate ATP-binding cassette transporter. The recognition event is mediated by the nucleotide-binding domain polypeptide of the transporter, which possesses a serotype-specific carbohydrate-binding module that only binds terminated O-PS chains. The WbdD terminator plays an additional pivotal structural role in recruiting WbdA to the membrane. The stoichiometry of WbdA:WbdD in active complexes is a critical factor in establishing the chain length distribution of the resulting glycans. The size of the O9a polysaccharide is determined by the chain-terminating dual kinase/methyltransferase (WbdD) that is tethered to the membrane and recruits polymerase/glycosyltransferase WbdA into an active enzyme complex by protein-protein interactions. Identification via bacterial two-hybrid analysis of a surface-exposed alpha-helix in the C-terminal mannosyltransferase domain of WbdA as the site of interaction with WbdD, the C-terminal domain was unable to interact with WbdD in the absence of its N-terminal partner. The WbdD protein orchestrates critical localization and coordination of activities involved in chain extension and termination. Complex domain interactions are needed to position the polymerase components appropriately for assembly into a functional complex located at the cytoplasmic membrane. WbdD is therefore a central player in a sophisticated quality control system that dictates the distribution of chain lengths and marks those chains with a terminal export tag
physiological function
the glycan of the polymannose O-polysaccharide of Escherichia coli O9a is assembled on a 55-carbon lipid acceptor (undecaprenyl phosphate) in the inner (cytoplasmic) membrane. Chain extension is mediated by three mannosyltransferases, designated WbdCBA, and occurs by the addition of mannose residues to the non-reducing terminus of the glycan. The chain length of the O9a O-polysaccharide is controlled by the activity of the WbdD protein by addition of methylphosphate to the non-reducing terminus
physiological function
the glycan of the polymannose O-polysaccharide of Escherichia coli O9a is assembled on a 55-carbon lipid acceptor (undecaprenyl phosphate) in the inner (cytoplasmic) membrane. Chain extension is mediated by three mannosyltransferases, designated WbdCBA, and occurs by the addition of mannose residues to the non-reducing terminus of the glycan. The chain length of the O9a O-polysaccharide is controlled by the activity of the WbdD protein by addition of methylphosphate to the non-reducing terminus; the WbdD proteins control the chain length of the Escherichia coli O9a polymannan by modifying the nonreducing end of nascent undecaprenol diphosphate-linked polymer. Overexpression of WbdD decreases O-polysaccharide chain length. WbdD activity coordinates polymannan chain termination with export across the inner membrane; WbdD controls polymerization reaction in biosynthesis of the O-polysaccharide by coordinating the correct membrane association required for activity of one of the critical mannosyltransferases, WbdA. Identification of regions in the C terminus of WbdD that contribute to the interaction
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physiological function
the WbdD proteins control the chain length of the Escherichia coli O9a polymannan by modifying the nonreducing end of nascent undecaprenol diphosphate-linked polymer. Overexpression of WbdD decreases O-polysaccharide chain length. WbdD activity coordinates polymannan chain termination with export across the inner membrane
physiological function
WbdD controls polymerization reaction in biosynthesis of the O-polysaccharide by coordinating the correct membrane association required for activity of one of the critical mannosyltransferases, WbdA. Identification of regions in the C terminus of WbdD that contribute to the interaction
Results 1 - 8 of 8