title: Protein D, the immunoglobulin D-binding protein of Haemophilus influenzae, is a lipoprotein.
abstract: Protein D is an immunoglobulin D-binding membrane protein exposed on the surface of the gram-negative bacterium Haemophilus influenzae. Results reported here indicate that protein D is a lipoprotein. The protein is apparently synthesized as a precursor with an 18-residue-long signal sequence modified by the covalent attachment of both ester-linked and amide-linked palmitate to the cysteine residue, which becomes the amino terminus after cleavage of the signal sequence. Globomycin inhibited maturation of protein D in H. influenzae, implying that protein D is exported through the lipoprotein export pathway. A mutant expressing a protein D lacking the cysteine residue was constructed by oligonucleotide site-directed mutagenesis. The mutated protein D molecule was not acylated and partitioned in the aqueous phase after Triton X-114 extraction of intact bacteria, unlike native and recombinant protein D, which partitioned in the detergent phase. The nonacylated protein D molecule was localized to the periplasmic space of Escherichia coli. The hydrophilic protein D molecule will be used in investigations concerning its ability to function as a vaccine component.
authors.affiliation: Department of Medical Microbiology, University of Lund, Malmö General Hospital, Sweden.
authors.forename: H
authors.initials: H
authors.lastname: Janson
authors.forename: L O
authors.initials: LO
authors.lastname: Hedén
authors.forename: A
authors.initials: A
authors.lastname: Forsgren
mesh_terms: D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D001483:Base Sequence; D015153:Blotting, Western; D002352:Carrier Proteins / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics; D002458:Cell Fractionation; D006193:Haemophilus influenzae; D007072:Immunoglobulin D; D008074:Lipoproteins / Q000737:chemistry*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D015345:Oligonucleotide Probes; D010455:Peptides / Q000494:pharmacology; D012689:Sequence Homology, Nucleic Acid
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D002352:Carrier Proteins; D007072:Immunoglobulin D; D008074:Lipoproteins; D015345:Oligonucleotide Probes; D010455:Peptides; C017339:globomycin; C067989:glpQ protein, Haemophilus influenzae