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Table 2 Main protein candidates for serodiagnosis that have been cross-validated by proteomic studies

From: Proteomics paves the way for Q fever diagnostics

Protein (locus-tag) Identification MW (kDa) pI Protein function Nature of protein Peptide signal sequence Nature of analyzed samples DT Clinical significance Reference(s)
CBU_0952 Acute disease antigen A (adaA) 25.9 8.67 Unknown Membrane MKKLTVTFLTFISIFFAATAAFA Cb isolates BT, IP Marker of acute Q fever [31, 63]
CBU_0612 Putative outer membrane chaperone protein (ompH, Skp) 18.8 9.71 Molecular chaperone, interacts with unfolded proteins Membrane* MIKRLLSAICLSVAMIWSVAAVAQTVGLVD Patient sera, Cb NM II TPE IP, RP Marker of Q fever endocarditis, SP with Q fever patients (general) [56, 57]
CBU_0937 Hypothetical protein 51.4 8.99 Unknown Membrane MTSKLVISALGLCVSGALSTTLAST mAbs, Cb NM II TPE, RP-based ELISA/HS IP, BT Marker of Q fever endocarditis. Marker of phase II [17, 56, 58]
CBU_1910 Outer membrane protein (com1) 27.6 9.08 Protein disulfide oxidoreductase, unknown role in pathogenesis Membrane MKNRLTALFLAGTLTAGVAIAAPSQF mAbs, Cb NM II TPE IP, BT, RP SP with both acute Q fever and Q fever endocarditis. Marker of both phase I and phase II [17, 58, 65, 6769]
CBU_0236 Elongation factor Tu (tuf-2) 43.5 5.32 GTP-dependent binding of aminoacyl-tRNA in protein biosynthesis Soluble*   mAbs, TPE Cb NM II, HS, AS (infected/vaccinated guinea pigs) IP SP, marker of acute Q fever [31, 58, 65, 68]
CBU_0092 Tol-pal system protein (YbgF) 34.3 6.46 Critical for maintaining integrity of bacterial outer membrane Involved in protein-protein interactions Membrane MRLIKMKIKTLCVSSALAALMLSAPLTWADA TPE Cb NM I and II HS Q-fever (general), AS (immunized guinea pigs) protein microarray IP, RP Phase II-specific marker (early diagnosis of acute Q fever), marker of Q fever (general) [68, 69]
CBU_0311 Outer membrane porin (Coxiella porin P1) 26.8 8.44 Able to form pore in lipid bilayers Membrane* OM location shown for Cb NM I METTTKLAIGVSALCCLASAAFAGGPD ELISA and ELISPOT based on RP/AS IP: HS, and AS (infected/vaccinated guinea pigs) RP, IP Marker of Q fever (general), marker of acute Q fever; applications for drug and vaccine development [31, 67]
CBU_1718 Chaperonin (GroL) 58.284 5.14 Protein folding, ATP hydrolysis Soluble   HS/TPE Cb NM II/RP; IP HS, and AS (infected/vaccinated guinea pigs) IP, RP Marker of Q fever (general), marker of acute Q fever [31, 65]
CBU_0229 50S ribosomal protein L7/L12 (RplJ) 13.2 4.71 Binding site for several factors in protein synthesis Membrane MAQLSKDDILEAVANMSVMDVVDLVKAMEEKFGVSAQAAIAVAGPVAGGEA IP: HS, and AS (infected/vaccinated guinea pigs) BT, IP Marker of both phase I and phase II, marker of acute Q fever [17, 31]
CBU_0263 DNA-directed RNA polymerase subunit alpha (rpoA) 35.5 5.61 DNA-dependent RNA polymerase transcription Soluble   OMP fraction of Cb NM II and CbuG_Q212 II; Phase 1 HS (chronic ) IP Marker of chronic Q fever [2, 69]
CBU_1916 Universal stress protein family 15.78 6.58 Stress response Soluble*   OMP fraction of Cb NM II and CbuG_Q212 II; Phase 1 HS (chronic) IP Marker of chronic Q fever [1, 69]
  1. I, phase I; II, phase II; AS, animal sera; BT, biotyping; Cb, Coxiella burnetii; DT, discovery technology; HS, human sera; IP, immunoproteomics; mAb, monoclonal antibody; MW, molecular weight; NM, Nine Mile; OM, outer membrane; OMP, outer membrane protein; pI, isoelectric point; RP, recombinant protein-based approaches; SP, seroreactive proteins; TPE, total protein extract.
  2. Soluble (cytosolic). Membrane (having a signal peptide that directs protein to the cell membrane). *More than two-fold more abundant in the LCV stage than in the SCV stage. Proteins common to SCV and LCV.