Abstract
The characterization of proteins from Brucella spp, the causative agent of brucellosis, has been the subject of intensive research. We have described an 18-kDa cytoplasmic protein of Brucella abortus and shown the potential usefulness of this protein as an antigen for the serologic diagnosis of brucellosis. The amino acid sequence of the protein showed a low but significant homology with that of lumazine synthases. Lumazine is an intermediate product in bacterial riboflavin biosynthesis. The recombinant form of the 18-kDa protein (expressed in E. coli) folds like the native Brucella protein and has lumazine-synthase enzymatic activity. Three-dimensional analysis by X-ray crystallography of the homolog Bacillus subtilis lumazine synthase has revealed that the enzyme forms an icosahedral capsid. Recombinant lumazine synthase from B. abortus was crystallized, diffracted X rays to 2.7-A resolution at room temperature, and the structure successfully solved by molecular replacement procedures. The macromolecular assembly of the enzyme differs from that of the enzyme from B. subtilis. The Brucella enzyme remains pentameric (90 kDa) in its crystallographic form. Nonetheless, the active sites of the two enzymes are virtually identical at the structural level, indicating that inhibitors of these enzymes could be viable pharmaceuticals across a broad species range. We describe the structural reasons for the differences in their quaternary arrangement and also discuss the potential use of this protein as a target for the development of acellular vaccines.
Highlights
The sequence, structure and function of protein components of microorganisms represent a field of increasing interest to both microbiologists and immunologists
We have found serum reactivity to cytosolic proteins (CP) in brucellosis patients [4] and in cows [5], sheep, goats, pigs and dogs [6] infected with different Brucella species, which suggests that the internal antigens are common to all the Brucella species regardless of the type of LPS
The 6,7-dimethyl-8-ribityllumazine synthase activity found in the cell extract was approximately 6-fold higher than the activity displayed by control bacteria, clearly indicating that the recombinant Brucella 18kDa protein is an enzyme with lumazine synthase activity [11]
Summary
The sequence, structure and function of protein components of microorganisms represent a field of increasing interest to both microbiologists and immunologists. The characterization of proteins from pathogenic bacteria can help to understand the interaction between the bacterium and the host and to study the humoral and cellular immune responses elicited during the infection. Proteins can be useful as specific antigens for the serologic diagnosis of bacterial infections and as specific targets for rational drug design of chemotherapeutic agents
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Schedule a callMore From: Brazilian journal of medical and biological research = Revista brasileira de pesquisas medicas e biologicas
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