ADPglucose pyrophosphorylase's N-terminus: structural role in allosteric regulation.
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.
Bejar
C M
CM
Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA.
Ballicora
M A
MA
Iglesias
A A
AA
Preiss
J
J
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
D029968:Escherichia coli Proteins; D051599:Glucose-1-Phosphate Adenylyltransferase