title: Extracellular secretion of pullulanase is unaffected by minor sequence changes but is usually prevented by adding reporter proteins to its N- or C-terminal end.
abstract: Linker insertions in the pullulanase structural gene (pulA) were examined for their effects on pullulanase activity and cell surface localization in Escherichia coli carrying the cognate secretion genes from Klebsiella oxytoca. Of the 23 insertions, 11 abolished pullulanase activity but none were found to prevent secretion. To see whether more drastic changes affected secretion, we fused up to five reporter proteins (E. coli periplasmic alkaline phosphatase, E. coli periplasmic maltose-binding protein, periplasmic TEM beta-lactamase, Erwinia chrysanthemi extracellular endoglucanase Z, and Bacillus subtilis extracellular levansucrase) to three different positions in the pullulanase polypeptide: close to the N terminus of the mature protein, at the C terminus of the protein, or at the C terminus of a truncated pullulanase variant lacking the last 256 amino acids. Only 3 of the 13 different hybrids were efficiently secreted: 2 in which beta-lactamase was fused to the C terminus of full-length or truncated pullulanase and 1 in which maltose-binding protein was fused close to the N terminus of pullulanase. Affinity-purified endoglucanase-pullulanase and pullulanase-endoglucanase hybrids exhibited apparently normal levels of pullulanase activity, indicating that the conformation of the pullulanase segment of the hybrid had not been dramatically altered by the presence of the reporter. However, pullulanase-endoglucanase hybrids were secreted efficiently if the endoglucanase component comprised only the 60-amino-acid, C-terminal cellulose-binding domain, suggesting that at least one factor limiting hybrid protein secretion might be the size of the reporter.
authors.affiliation: Unité de Génétique Moléculaire (Centre National de la Recherche Scientifique URA1149, Institut Pasteur, Paris, France.
authors.forename: N
authors.initials: N
authors.lastname: Sauvonnet
authors.forename: I
authors.initials: I
authors.lastname: Poquet
authors.forename: A P
authors.initials: AP
authors.lastname: Pugsley
mesh_terms: D018528:ATP-Binding Cassette Transporters; D000469:Alkaline Phosphatase / Q000235:genetics; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics; D002480:Cellulase / Q000235:genetics; D019286:Endopeptidase K; D004926:Escherichia coli / Q000235:genetics; D029968:Escherichia coli Proteins; D005798:Genes, Bacterial / Q000235:genetics; D017930:Genes, Reporter; D006026:Glycoside Hydrolases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006602:Hexosyltransferases / Q000235:genetics; D007709:Klebsiella / Q000201:enzymology / Q000235:genetics; D058619:Maltose-Binding Proteins; D008969:Molecular Sequence Data; D009004:Monosaccharide Transport Proteins; D016254:Mutagenesis, Insertional; D033902:Periplasmic Binding Proteins; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012697:Serine Endopeptidases; D001618:beta-Lactamases / Q000235:genetics
chemical_list: D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; C461619:MalE protein, E coli; D058619:Maltose-Binding Proteins; D009004:Monosaccharide Transport Proteins; D033902:Periplasmic Binding Proteins; D011993:Recombinant Fusion Proteins; C461599:maltose transport system, E coli; D006602:Hexosyltransferases; C021513:levansucrase; D000469:Alkaline Phosphatase; D006026:Glycoside Hydrolases; C080692:endoglucanase Z; D002480:Cellulase; C100181:pullulanase; D012697:Serine Endopeptidases; D019286:Endopeptidase K; D001618:beta-Lactamases