title: ADPglucose pyrophosphorylase's N-terminus: structural role in allosteric regulation.
abstract: We studied the functional role of the Escherichia coli ADPglucose pyrophosphorylase's N-terminus in allosteric regulation, and the particular effects caused by its length. Small truncated mutants were designed, and those lacking up to 15-residues were active and highly purified for further kinetic analyses. Ndelta3 and Ndelta7 did not change the kinetic parameters with respect to the wild-type. Ndelta11 and Ndelta15 enzymes were insensitive to allosteric regulation and highly active in the absence of the activator. Co-expression of two polypeptides corresponding to the N- and C-termini generated an enzyme with activation properties lower than those of the wild-type [C.M. Bejar, M.A. Ballicora, D.F. Gómez Casati, A.A. Iglesias, J. Preiss, The ADPglucose pyrophosphorylase from Escherichia coli comprises two tightly bound distinct domains, FEBS Lett. 573 (2004) 99-104]. Here, we characterized a Ndelta15 co-expression mutant, in which the allosteric regulation was restored to wild-type levels. Unusual allosteric effects caused by either an N-terminal truncation or co-expression of individual domains may respond to structural changes favoring an up-regulated or a down-regulated conformation rather than specific activator or inhibitor sites' disruption.
authors.affiliation: Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA.
authors.forename: C M
authors.initials: CM
authors.lastname: Bejar
authors.forename: M A
authors.initials: MA
authors.lastname: Ballicora
authors.forename: A A
authors.initials: AA
authors.lastname: Iglesias
authors.forename: J
authors.initials: J
authors.lastname: Preiss
mesh_terms: D000494:Allosteric Regulation / Q000235:genetics; D000595:Amino Acid Sequence; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D051599:Glucose-1-Phosphate Adenylyltransferase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017384:Sequence Deletion
chemical_list: D029968:Escherichia coli Proteins; D051599:Glucose-1-Phosphate Adenylyltransferase