The 18-kDa cytoplasmic protein of Brucella species - an antigen useful for diagnosis - is a lumazine synthase

• Published in: Journal of medical microbiology Vol. 48; no. 9; pp. 833 - 839
• Main Authors: Goldbaum, Fernando A, Velikovsky, Carlos A, Baldi, Pablo C, Mortl, Simone, Bacher, Adelbert, Fossati, Carlos A
• Format: Journal Article
• Language: English
• Published: Reading Soc General Microbiol 01-09-1999; Society for General Microbiology
• Subjects: Amino Acid Sequence; Animals; Antibodies, Bacterial - blood; Antigens, Bacterial - immunology; Bacterial diseases; Bacterial Outer Membrane Proteins - chemistry; Bacterial Outer Membrane Proteins - genetics; Bacterial Outer Membrane Proteins - immunology; Bacterial Outer Membrane Proteins - metabolism; Bacteriological methods and techniques used in bacteriology; Bacteriology; Biological and medical sciences; Brucella; Brucella - enzymology; Brucella - genetics; Enzyme-Linked Immunosorbent Assay; Escherichia coli; Escherichia coli - genetics; Escherichia coli - metabolism; Fundamental and applied biological sciences. Psychology; Human bacterial diseases; Humans; Immunoblotting; Infectious diseases; Lipoproteins; lumazine synthase; Medical sciences; Microbiology; Miscellaneous; Molecular Sequence Data; Multienzyme Complexes - chemistry; Multienzyme Complexes - immunology; Multienzyme Complexes - metabolism; Protein Folding; Recombinant Proteins - chemistry; Recombinant Proteins - immunology; Recombinant Proteins - metabolism; Sequence Homology, Amino Acid; Human; Nucleotide sequence; Enzyme; Brucella; Homology; Serology; Method; Protein; Infection; Brucellaceae; Enzymatic activity; Animal; Bacteriosis; Bacteria; Brucellosis; Diagnosis; Detection; Aminoacid sequence
• ISSN: 0022-2615; 1473-5644
• DOI: 10.1099/00222615-48-9-833

1 Instituto de Estudios de la Inmunidad Humoral (IDEHU), Facultad de Farmacia y Bioquímica UBA, Junin 956 4to. piso, 1113 Buenos Aires, Argentina
* Department of Chemistry, Technical University of Munich, Lichtenbergstrasse 4, D-85747, Garching, Germany
2 Corresponding author: Dr F. A. Goldbaum. Present address: Instituto de Investigaciones Bioquimicas ‘Fundación Campomar’, Av. Patricias Argentinas 435, 1405 Buenos Aires, Argentina (e-mail: [e-mail]).
Received July 2, 1998
Revision received October 6, 1998.
Accepted December 8, 1998
Previous studies have shown that the detection of antibodies to an 18-kDa cytoplasmic protein of Brucella spp. is useful for the diagnosis of human and animal brucellosis. This protein has now been expressed in recombinant form in Escherichia coli . The recombinant protein is soluble only under reducing conditions, but alkylation with iodo-acetamide renders it soluble in non-reducing media. As shown by gel exclusion chromatography, this soluble form arranges in pentamers of 90 kDa. The reactivity of human and animal sera against the recombinant protein was similar to that found with the native protein present in brucella cytoplasmic fraction, suggesting that the recombinant protein is correctly folded. The protein has low but significant homology (30%) with lumazine synthases involved in bacterial riboflavin biosynthesis, which also arrange as pentamers. Biological tests on the crude extract of the recombinant bacteria and on the purified recombinant protein showed that the biological activity of the Brucella spp. 18-kDa protein is that of lumazine synthase. Preliminary crystallographic analysis showed that the Brucella spp. lumazine synthase arranges in icosahedric capsids similar to those formed by the lumazine synthases of other bacteria. The high immunogenicity of this protein, potentially useful for the design of acellular vaccines, could be explained by this polymeric arrangement.