title: Outer membrane lipoprotein e (P4) of Haemophilus influenzae is a novel phosphomonoesterase.
abstract: Haemophilus influenzae exists as a commensal of the upper respiratory tract of humans but also causes infections of contiguous structures. We describe the identification, localization, purification, and characterization of a novel, surface-localized phosphomonoesterase from a nontypeable H. influenzae strain, R2866. Sequences obtained from two CNBr-derived fragments of this protein matched lipoprotein e (P4) within the H. influenzae sequence database. Escherichia coli DH5alpha transformed with plasmids containing the H. influenzae hel gene, which encodes lipoprotein e (P4), produced high levels of a membrane-associated phosphomonoesterase. The isolated approximately 28-kDa enzyme was tartrate resistant and displayed narrow substrate specificity with the highest activity for arylphosphates, excluding 5-bromo-4-chloro-3-indolylphosphate. Optimum enzymatic activity was observed at pH 5.0 and only in the presence of divalent copper. The enzyme was inhibited by vanadate, molybdate, and EDTA but was resistant to inorganic phosphate. The association of phosphomonoesterase activity with a protein that has also been recognized as a heme transporter suggests a unique role for this unusual phosphohydrolase.
authors.affiliation: Department of Molecular Microbiology and Immunology, University of Missouri Medical School, Columbia, Missouri 65212, USA.
authors.forename: T J
authors.initials: TJ
authors.lastname: Reilly
authors.forename: D L
authors.initials: DL
authors.lastname: Chance
authors.forename: A L
authors.initials: AL
authors.lastname: Smith
mesh_terms: D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D002413:Cations, Divalent / Q000378:metabolism; D002847:Chromatography, Agarose; D003001:Cloning, Molecular; D004591:Electrophoresis, Polyacrylamide Gel; D004950:Esterases; D006193:Haemophilus influenzae / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D006801:Humans; D008074:Lipoproteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D010744:Phosphoric Monoester Hydrolases / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D001425:Bacterial Outer Membrane Proteins; D002413:Cations, Divalent; D008074:Lipoproteins; C098614:e(P4) lipoprotein, Haemophilus influenzae; D004950:Esterases; D010744:Phosphoric Monoester Hydrolases