Blackmore, T.Hellwage, J.Sadlon, T.Higgs, N.Zipfel, P.Ward, H.Gordon, D.2014-01-242014-01-241998Journal of Immunology, 1998; 160(7):3342-33480022-17671550-6606http://hdl.handle.net/2440/81790Complement factor H (fH) regulates activation of the alternative pathway of C, reducing the amount of C3b deposited on sialic acid-rich surfaces. Heparin binding has been used as a model for examining the sialic acid- binding characteristics of fH. We have previously shown thai of the 20 short consensus repeat (SCR) modules of fH, SCR 7 contains an important heparin binding site, but other SCRs also play a role in heparin binding. To localize the other sites, we prepared recombinant truncated and SCR deletion mutants of fH and tested them by heparin-agarose affinity chromatography. The 5 C- terminal SCRs were found to contain a heparin binding site as an SCR 7 deletion mutant of the N terminal 15 SCRs did not bind heparin, but a construct consisting of SCRs 16-20 was shown to bind heparin. Double deletion of SCRs 7 and 20 fH abrogated binding to heparin, indicating that SCR 20 contains a heparin binding site. This finding was confirmed with the observation that attachment of SCR 20 to a group of nonbinding SCRs produced a heparin-binding protein. A protein consisting of SCRs 19 and 20 did not bind heparin, whereas SCRs 18-20 did, indicating that, although SCR 20 contains a heparin binding site, at least two nonspecific adjacent SCRs are required. fH-related protein-3 (FHR-3) possesses an SCR homologous to SCR 7 of fH and bound heparin, whereas FHR-4, which lacks such an SCR, did not. Thus, fH contains two separate heparin binding sites which are located in SCRs 7 and 20.enCopyright © 1998 by The American Association of ImmunologistsHumansHeparinApolipoproteinsBlood ProteinsComplement Factor HRecombinant ProteinsSequence DeletionBinding SitesRepetitive Sequences, Nucleic AcidConsensus SequenceProtein Structure, TertiaryJournal article00300002202014012408125610.4049/jimmunol.160.7.334211 Medical and Health Sciences1107 Immunology110706 Immunogenetics (incl. Genetic Immunology)0000727001000342-s2.0-003205519664226Ward, H. [0000-0002-3831-1205]