title: A recombinant two-module form of human properdin is an inhibitor of the complement alternative pathway.
abstract: Properdin upregulates the alternative complement pathway by binding and stabilising the C3 convertase complex (C3bBb). Properdin is a soluble glycoprotein and its flexible rod-like 53kDa monomers form cyclic polymers (dimers, trimers, tetramers and pentamers). The properdin monomer consists of seven thrombospondin type I repeats (TSR 0-6), which are similar and homologous to domains found in circumsporozoite and thrombospondin-related anonymous proteins of Plasmodium species, ETP100 of Eimeria tenella, various complement components C6-C9, and thrombospondin I and II. Using deletion constructs, TSR4 and TSR5 of human properdin were implicated in C3b binding and stabilising C3 convertase. However, individually expressed TSR4 or TSR5 failed to bind properdin ligands. Here, we have expressed and characterized biologically active TSR4 and TSR5 together (TSR4+5) in tandem in Escherichia coli, fused to maltose-binding protein. MBP-TSR4+5 bind solid-phase C3b, sulfatides and glycosaminoglycans. In addition, functionally active recombinant TSR4+5 modules inhibit the alternative pathway of complement.
authors.affiliation: Biosciences, College of Health and Life Sciences, Brunel University London, Uxbridge UB8 3PH, UK.
authors.forename: Lubna
authors.initials: L
authors.lastname: Kouser
authors.affiliation: Biosciences, College of Health and Life Sciences, Brunel University London, Uxbridge UB8 3PH, UK; Department of Pharmacology, University of Oxford, Oxford OX1 3QT, UK.
authors.forename: Munirah
authors.initials: M
authors.lastname: Abdul-Aziz
authors.affiliation: Biosciences, College of Health and Life Sciences, Brunel University London, Uxbridge UB8 3PH, UK.
authors.forename: Anthony G
authors.initials: AG
authors.lastname: Tsolaki
authors.affiliation: Biosciences, College of Health and Life Sciences, Brunel University London, Uxbridge UB8 3PH, UK.
authors.forename: Dipti
authors.initials: D
authors.lastname: Singhal
authors.affiliation: Department of Infection, Immunity and Inflammation, Maurice Shock Medical Sciences Building, University Road, Leicester, LE1 9HN, UK.
authors.forename: Wilhelm J
authors.initials: WJ
authors.lastname: Schwaeble
authors.affiliation: Liverpool School of Tropical Medicine, Pembroke Place Liverpool, L3 5QA, UK.
authors.forename: Britta C
authors.initials: BC
authors.lastname: Urban
authors.affiliation: Department of Biochemistry, College of Science, King Saud University, Riyadh, Saudi Arabia.
authors.forename: Haseeb A
authors.initials: HA
authors.lastname: Khan
authors.affiliation: Department of Pharmacology, University of Oxford, Oxford OX1 3QT, UK; Department of Infection, Immunity and Inflammation, Maurice Shock Medical Sciences Building, University Road, Leicester, LE1 9HN, UK.
authors.forename: Robert B
authors.initials: RB
authors.lastname: Sim
authors.affiliation: Biosciences, College of Health and Life Sciences, Brunel University London, Uxbridge UB8 3PH, UK. Electronic address: uday.kishore@brunel.ac.uk.
authors.forename: Uday
authors.initials: U
authors.lastname: Kishore
mesh_terms: D015153:Blotting, Western; D003170:Complement Pathway, Alternative / Q000187:drug effects / Q000276:immunology*; D006801:Humans; D011414:Properdin / Q000276:immunology* / Q000494:pharmacology; D011994:Recombinant Proteins / Q000276:immunology
chemical_list: D011994:Recombinant Proteins; D011414:Properdin
keywords: Alternative pathway; Complement; Properdin; Recombinant; Thrombospondin