Protein D, the immunoglobulin D-binding protein of Haemophilus influenzae, is a lipoprotein

• 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.

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MEDICIN OCH HÄLSOVETENSKAP  -- Medicinska och farmaceutiska grundvetenskaper -- Mikrobiologi inom det medicinska området (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Basic Medicine -- Microbiology in the medical area (hsv//eng)

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