Bacteria Binding by DMBT1/SAG/gp-340 Is Confined to the VEVLXXXXW Motif in Its Scavenger Receptor Cysteine-rich Domains

The scavenger receptor cysteine-rich (SRCR) proteins form an archaic group of metazoan proteins characterized by the presence of SRCR domains. These proteins are classified in group A and B based on the number of conserved cysteine residues in their SRCR domains, i.e. six for group A and eight for group B. The protein DMBT1 (deleted in malignant brain tumors 1), which is identical to salivary agglutinin and lung gp-340, belongs to the group B SRCR proteins and is considered to be involved in tumor suppression and host defense by pathogen binding. In a previous study we used nonoverlapping synthetic peptides covering the SRCR consensus sequence to identify a 16-amino acid bacteria-binding protein loop (peptide SRCRP2; QGRVEVLYRGSWGTVC) within the SRCR domains. In this study, using overlapping peptides, we pinpointed the minimal bacteria-binding site on SRCRP2, and thus DMBT1, to an 11-amino acid motif (DMBT1 pathogen-binding site 1 or DMBT1pbs1; GRVEVLYRGSW). An alanine substitution scan revealed that VEVL and Trp are critical residues in this motif. Bacteria binding by DMBT1pbs1 was different from the bacteria binding by the macrophage receptor MARCO in which an RXR motif was critical. In addition, the homologous consensus sequences of a number of SRCR proteins were synthesized and tested for bacteria binding. Only consensus sequences of DMBT1 orthologues bound bacteria by this motif. The scavenger receptor cysteine-rich (SRCR) proteins form an archaic group of metazoan proteins characterized by the presence of SRCR domains. These proteins are classified in group A and B based on the number of conserved cysteine residues in their SRCR domains, i.e. six for group A and eight for group B. The protein DMBT1 (deleted in malignant brain tumors 1), which is identical to salivary agglutinin and lung gp-340, belongs to the group B SRCR proteins and is considered to be involved in tumor suppression and host defense by pathogen binding. In a previous study we used nonoverlapping synthetic peptides covering the SRCR consensus sequence to identify a 16-amino acid bacteria-binding protein loop (peptide SRCRP2; QGRVEVLYRGSWGTVC) within the SRCR domains. In this study, using overlapping peptides, we pinpointed the minimal bacteria-binding site on SRCRP2, and thus DMBT1, to an 11-amino acid motif (DMBT1 pathogen-binding site 1 or DMBT1pbs1; GRVEVLYRGSW). An alanine substitution scan revealed that VEVL and Trp are critical residues in this motif. Bacteria binding by DMBT1pbs1 was different from the bacteria binding by the macrophage receptor MARCO in which an RXR motif was critical. In addition, the homologous consensus sequences of a number of SRCR proteins were synthesized and tested for bacteria binding. Only consensus sequences of DMBT1 orthologues bound bacteria by this motif. The scavenger receptor cysteine-rich (SRCR) 1The abbreviations used are: SRCR, scavenger receptor cysteinerich; DMBT1, deleted in malignant brain tumors 1; DMBT1pbs1, DMBT1 pathogen binding site 1; DMBT1SAG, DMTB1 isoform secreted in the saliva; MSR1, macrophage scavenger receptor 1. proteins form an archaic group of metazoan proteins (1Resnick D. Pearson A. Krieger M. Trends Biochem. Sci. 1994; 19: 5-8Abstract Full Text PDF PubMed Scopus (310) Google Scholar, 2Pahler S. Blumbach B. Müller I. Müller W.E. J. Exp. Zool. 1998; 282: 332-343Crossref PubMed Scopus (54) Google Scholar, 3Müller W.E. Cell Tissue Res. 1997; 289: 383-395Crossref PubMed Scopus (97) Google Scholar, 4Freeman M. Ashkenas J. Rees D.J. Kingsley D.M. Copeland N.G. Jenkins N.A. Krieger M. Proc. Natl. Acad. Sci. U. S. A. 1990; 87: 8810-8814Crossref PubMed Scopus (262) Google Scholar, 5Aruffo A. Bowen M.A. Patel D.D. Haynes B.F. Starling G.C. Gebe J.A. Bajorath J. Immunol. Today. 1997; 18: 498-504Abstract Full Text PDF PubMed Scopus (130) Google Scholar). This group of glycoproteins comprises cell surface molecules as well as secreted proteins that are characterized by the presence of one or more SRCR domains. SRCR domains consist of ∼110 amino acids and are divided into groups A and B based on the number of conserved cysteine residues, namely six for group A and eight for group B. The best studied members of the group A SRCR proteins are the macrophage scavenger receptor (MSR1), the Mac 2-binding protein (Mac-2bp), and MARCO. Both MSR1 and MARCO are known to interact with bacteria (6Brännström A. Sankala M. Tryggvason K. Pikkarainen T. Biochem. Biophys. Res. Commun. 2002; 290: 1462-1469Crossref PubMed Scopus (60) Google Scholar, 7Dunne D.W. Resnick D. Greenberg J. Krieger M. Joiner K.A. Proc. Natl. Acad. Sci. U. S. A. 1994; 91: 1863-1867Crossref PubMed Scopus (306) Google Scholar). In contrast to MARCO (8Elomaa O. Sankala M. Pikkarainen T. Bergmann U. Tuuttila A. Raatikainen-Ahokas A. Sariola H. Tryggvason K. J. Biol. Chem. 1998; 273: 4530-4538Abstract Full Text Full Text PDF PubMed Scopus (121) Google Scholar), the SRCR domain of MSR1 does not seem to be involved in bacteria binding (9Doi T. Higashino K. Kurihara Y. Wada Y. Miyazaki T. Nakamura H. Uesugi S. Imanishi T. Kawabe Y. Itakura H. Yazaki Y. Matsumoto A. Kodama T. J. Biol. Chem. 1993; 268: 2126-2133Abstract Full Text PDF PubMed Google Scholar, 10Platt N. Gordon S. J. Clin. Investig. 2001; 108: 649-654Crossref PubMed Scopus (257) Google Scholar). Bacteria binding by MARCO involves an RXR motif within the SRCR domain, indicating that ionic interactions play a crucial role in the interaction with its negatively charged ligands (6Brännström A. Sankala M. Tryggvason K. Pikkarainen T. Biochem. Biophys. Res. Commun. 2002; 290: 1462-1469Crossref PubMed Scopus (60) Google Scholar). Group B SRCR proteins are generally involved in the regulation of cellular immune responses. In vertebrates, the group B SRCR proteins can be divided, on the basis of their structure and sequence homology, into three subgroups (11Grønlund J. Vitved L. Lausen M. Skjødt K. Holmskov U. J. Immunol. 2000; 165: 6406-6415Crossref PubMed Scopus (49) Google Scholar). The first subgroup includes CD5 (12Jones N.H. Clabby M.L. Dialynas D.P. Huang H.J. Herzenberg L.A. Strominger J.L. Nature. 1986; 323: 346-349Crossref PubMed Scopus (187) Google Scholar), CD6 (13Aruffo A. Melnick M.B. Linsley P.S. Seed B. J. Exp. Med. 1991; 174: 949-952Crossref PubMed Scopus (131) Google Scholar), and SPα (14Gebe J.A. Kiener P.A. Ring H.Z. Li X. Francke U. Aruffo A. J. Biol. Chem. 1997; 272: 6151-6158Abstract Full Text Full Text PDF PubMed Scopus (85) Google Scholar). CD5 and CD6 are composed of an extracellular region of three SRCR domains, a transmembrane region, and a cytoplasmic region. SPα lacks the latter two regions but contains three SRCR domains that are highly homologous to those of CD5 and CD6. These three proteins are mainly expressed by T-cells and B-cells (12Jones N.H. Clabby M.L. Dialynas D.P. Huang H.J. Herzenberg L.A. Strominger J.L. Nature. 1986; 323: 346-349Crossref PubMed Scopus (187) Google Scholar, 13Aruffo A. Melnick M.B. Linsley P.S. Seed B. J. Exp. Med. 1991; 174: 949-952Crossref PubMed Scopus (131) Google Scholar). The second subgroup of SRCR group B molecules is the workshop cluster 1 (WC1) family, which includes WC1, CD163, and M160 (11Grønlund J. Vitved L. Lausen M. Skjødt K. Holmskov U. J. Immunol. 2000; 165: 6406-6415Crossref PubMed Scopus (49) Google Scholar, 15Law S.K. Micklem K.J. Shaw J.M. Zhang X.P. Dong Y. Willis A.C. Mason D.Y. Eur. J. Immunol. 1993; 23: 2320-2325Crossref PubMed Scopus (218) Google Scholar). These molecules are primarily related to monocyte and macrophage cell lineages. CD163 scavenges haptoglobin-hemoglobin complexes (16Kristiansen M. Graversen J.H. Jacobsen C. Sonne O. Hoffman H.-J. Law S.K.A. Moestrop S.K. Nature. 2001; 409: 198-201Crossref PubMed Scopus (1299) Google Scholar). The third subgroup of group B SRCR proteins includes human DMBT1 (deleted in malignant brain tumors 1) (17Bikker F.J. Ligtenberg A.J.M. Nazmi K. Veerman E.C.I. Van't Hof W. Bolscher J.G.M. Poustka A. Nieuw Amerongen A.V. Mollenhauer J. J. Biol. Chem. 2002; 277: 32109-32115Abstract Full Text Full Text PDF PubMed Scopus (123) Google Scholar, 18Holmskov U. Lawson P. Teisner B. Tornøe I. Willis A.C. Morgan C. Koch C. Reid K.B. J. Biol. Chem. 1997; 272: 13743-13749Abstract Full Text Full Text PDF PubMed Scopus (192) Google Scholar, 19Kang W. Reid K.B. FEBS Lett. 2003; 540: 21-25Crossref PubMed Scopus (77) Google Scholar, 20Mollenhauer J. Wiemann S. Scheurlen W. Korn B. Hayashi Y. Wilgenbus K.K. von Deimling A. Poustka A. Nat. Genet. 1997; 17: 32-39Crossref PubMed Scopus (411) Google Scholar, 21Mollenhauer J. Holmskov U. Wiemann S. Krebs I. Herbertz S. Madsen J. Kioschis P. Coy J.F. Poustka A. Oncogene. 1999; 18: 6233-6240Crossref PubMed Scopus (75) Google Scholar, 22Prakobphol A. Xu F. Hoang V.M. Larsson T. Bergstrom J. Johansson I. Frängsmyr L. Holmskov U. Leffler H. Nilsson C. Borén T. Wright J.R. Strömberg N. Fisher S.J. J. Biol. Chem. 2000; 275: 39860-39866Abstract Full Text Full Text PDF PubMed Scopus (185) Google Scholar) with homologues in the rat (Ebnerin) (23Li X.J. Snyder S.H. J. Biol. Chem. 1995; 270: 17674-17679Abstract Full Text Full Text PDF PubMed Scopus (89) Google Scholar), mouse (CRP-ductin) (24Cheng H. Bjerknes M. Chen H. Anat. Rec. 1996; 244: 327-343Crossref PubMed Scopus (93) Google Scholar), rabbit (Hensin) (25Takito J. Yan L. Ma J. Hikita C. Vijayakumar S. Warburton D. Al Awqati Q. Am. J. Physiol. 1999; 277: F277-F289PubMed Google Scholar), and cow (bovine gallbladder mucin) (26Nunes D.P. Keates A.C. Afdhal N.H. Offner G.D. Biochem. J. 1995; 310: 41-48Crossref PubMed Scopus (34) Google Scholar). Pema-SRCR from the sea lamprey Pertromyzon marinus (27Mayer W.E. Tichy H. Gene. 1995; 164: 267-271Crossref PubMed Scopus (32) Google Scholar) is also included in this subgroup. Molecules of this subgroup are expressed by epithelial cells in the gastrointestinal tract and the ducts of the exocrine glands and are commonly secreted in mucosal fluids (28Bikker F.J. Ligtenberg A.J.M. van der Wal J.E. van den Keijbus P.A.M. Holmskov U. Veerman E.C.I. Nieuw Amerongen A.V. J. Dent. Res. 2002; 81: 134-139Crossref PubMed Google Scholar). They are associated with host defense, e.g. by pathogen binding, but also have been suggested as playing a role in epithelial differentiation (27Mayer W.E. Tichy H. Gene. 1995; 164: 267-271Crossref PubMed Scopus (32) Google Scholar). Salivary agglutinin and lung gp-340 are encoded by the gene DMBT1 on chromosome 10q25.3-q26.1 (18Holmskov U. Lawson P. Teisner B. Tornøe I. Willis A.C. Morgan C. Koch C. Reid K.B. J. Biol. Chem. 1997; 272: 13743-13749Abstract Full Text Full Text PDF PubMed Scopus (192) Google Scholar, 20Mollenhauer J. Wiemann S. Scheurlen W. Korn B. Hayashi Y. Wilgenbus K.K. von Deimling A. Poustka A. Nat. Genet. 1997; 17: 32-39Crossref PubMed Scopus (411) Google Scholar, 22Prakobphol A. Xu F. Hoang V.M. Larsson T. Bergstrom J. Johansson I. Frängsmyr L. Holmskov U. Leffler H. Nilsson C. Borén T. Wright J.R. Strömberg N. Fisher S.J. J. Biol. Chem. 2000; 275: 39860-39866Abstract Full Text Full Text PDF PubMed Scopus (185) Google Scholar, 29Ligtenberg T.J.M. Bikker F.J. Groenink J. Tornøe I. Leth-Larsen R. Veerman E.C.I. Nieuw Amerongen A.V. Holmskov U. Biochem. J. 2001; 359: 243-248Crossref PubMed Scopus (78) Google Scholar, 30Holmskov U. Mollenhauer J. Madsen J. Vitved L. Grønlund J. Tornøe I. Kliem A. Reid K.B. Poustka A. Skjødt K. Proc. Natl. Acad. Sci. U. S. A. 1999; 96: 10794-10799Crossref PubMed Scopus (189) Google Scholar). These proteins represent the DMBT1 isoforms secreted in the saliva (DMBT1SAG) and the lung fluid (DMBT1GP340), respectively. For about two decades DMBT1SAG, which manifests a broad bacteria binding spectrum, has been intensively investigated with regard to its role in caries prevention by binding and agglutination of cariogenic bacteria in the oral cavity (31Carlén A. Bratt P. Stenudd C. Olsson J. Strömberg N. J. Dent. Res. 1998; 77: 81-90Crossref PubMed Scopus (52) Google Scholar, 32Ericson T. Rundegren J. Eur. J. Biochem. 1983; 133: 255-261Crossref PubMed Scopus (119) Google Scholar). DMBT1GP340 is putatively involved in respiratory tract protection because it interacts with the defense collectin surfactant proteins D (SP-D) and A (SP-A) and is able to stimulate alveolar macrophage migration (18Holmskov U. Lawson P. Teisner B. Tornøe I. Willis A.C. Morgan C. Koch C. Reid K.B. J. Biol. Chem. 1997; 272: 13743-13749Abstract Full Text Full Text PDF PubMed Scopus (192) Google Scholar, 33Tino M.J. Wright J.R. Am. J. Respir. Cell Mol. Biol. 1999; 20: 759-768Crossref PubMed Scopus (92) Google Scholar). By initial protein digestion and utilization of non-overlapping synthetic peptides, we recently identified a protein loop in the SRCR domains of DMBT1 that was able to bind to various bacteria (16Kristiansen M. Graversen J.H. Jacobsen C. Sonne O. Hoffman H.-J. Law S.K.A. Moestrop S.K. Nature. 2001; 409: 198-201Crossref PubMed Scopus (1299) Google Scholar). The use of synthetic peptides thus offered us a simple in vitro system to explore fundamental aspects of DMBT1- and SRCR-mediated bacteria binding in general. In this study we have defined the minimal bacteria-binding motif on DMBT1 as an 11-mer peptide designated DMBT1pbs1 (DMBT1 pathogen-binding site 1). By an alanine substitution scan, critical amino acid residues within this motif were identified. Consensus peptides were derived from the DMBT1pbs1-corresponding regions of other SRCR proteins. Only the peptides derived from DMBT1 and its orthologues showed significant bacterial binding. Purification of DMBT1SAG—DMBT1SAG was purified by gel filtration as described previously (29Ligtenberg T.J.M. Bikker F.J. Groenink J. Tornøe I. Leth-Larsen R. Veerman E.C.I. Nieuw Amerongen A.V. Holmskov U. Biochem. J. 2001; 359: 243-248Crossref PubMed Scopus (78) Google Scholar). DMBT1SAG was eluted from a Sephacryl S-400 HR column (Amersham Biosciences) with either phosphate-buffered saline or Tris-buffered saline (10 mm Tris-HCl and 150 mm NaCl, pH 7.4). Bacteria—Streptococcus mutans (Ingbritt), Streptococcus gordonii (HG222), and Escherichia coli (OM36–1) were cultured on blood agar plates under anaerobic conditions with 5% CO2 at 37 °C for 48 h. Subsequently, single colonies of S. mutans and S. gordonii were cultured in Todd Hewitt medium (Oxoid, Hampshire, United Kingdom). Single colonies of E. coli were cultured in Luria Broth (Oxoid) at 37 °C for 24 h in air/CO2 (19:1). Cells were harvested and washed twice in Tris-buffered saline supplemented with 0.1% (v/v) and 1 mm was cultured on plates (Oxoid) at 37 °C for h. H. was harvested by the plates and washed twice in mm pH supplemented with 0.1% (v/v) and 1 mm Bacteria were in to a of with and synthetic peptides were SRCR domain and as described previously using (17Bikker F.J. Ligtenberg A.J.M. Nazmi K. Veerman E.C.I. Van't Hof W. Bolscher J.G.M. Poustka A. Nieuw Amerongen A.V. Mollenhauer J. J. Biol. Chem. 2002; 277: 32109-32115Abstract Full Text Full Text PDF PubMed Scopus (123) Google Scholar). For of the minimal bacteria binding site we synthesized overlapping peptides covering the SRCR consensus sequence from six amino acids the amino (peptide to six amino acids the to study the role of the amino acids in pathogen binding, we synthesized a of peptides in which in its was for alanine substitution identify sequences in other SRCR the was using or the as the which us to the SRCR Consensus sequences of the SRCR domains in proteins were with (17Bikker F.J. Ligtenberg A.J.M. Nazmi K. Veerman E.C.I. Van't Hof W. Bolscher J.G.M. Poustka A. Nieuw Amerongen A.V. Mollenhauer J. J. Biol. Chem. 2002; 277: 32109-32115Abstract Full Text Full Text PDF PubMed Scopus (123) Google Scholar). by was with a peptide as described the of peptides was (17Bikker F.J. Ligtenberg A.J.M. Nazmi K. Veerman E.C.I. Van't Hof W. Bolscher J.G.M. Poustka A. Nieuw Amerongen A.V. Mollenhauer J. J. Biol. Chem. 2002; 277: 32109-32115Abstract Full Text Full Text PDF PubMed Scopus (123) Google Scholar). The of the peptides was by of on a United as described previously M. Li Eur. J. Biochem. 2001; 268: PubMed Scopus Google Scholar). The peptides used in the of were from and a of at binding by DMBT1pbs1 homologous peptides of other SRCR domain human domain human domain rabbit (DMBT1 domain mouse (DMBT1 rat (DMBT1 sequences other sequences are consensus sequences and sequences within the SRCR binding protein sequences other sequences are consensus sequences and sequences within the SRCR sequences other sequences are consensus sequences and sequences within the SRCR Consensus sequences other sequences are consensus sequences and sequences within the SRCR proteins. in a was using a based on the of with binding as (17Bikker F.J. Ligtenberg A.J.M. Nazmi K. Veerman E.C.I. Van't Hof W. Bolscher J.G.M. Poustka A. Nieuw Amerongen A.V. Mollenhauer J. J. Biol. Chem. 2002; 277: 32109-32115Abstract Full Text Full Text PDF PubMed Scopus (123) Google Scholar, J.A. Veerman E.C.I. M. K. Bolscher J.G.M. Nieuw Amerongen A.V. J. 2003; PubMed Scopus Google Scholar, in Scholar). plates were with various of either synthetic peptides or purified The peptides were in mm pH to a of and at °C for the plates were washed twice with the Subsequently, of a bacterial were to well and at 37 °C for h. were washed three with the using a bacteria were using a cell and were in the at the for and washed three with the was in a at and These were at three of a bacterial were with of peptide at peptide of in plates and at 37 °C for was of the agglutination was with a United using 150 peptide as described (17Bikker F.J. Ligtenberg A.J.M. Nazmi K. Veerman E.C.I. Van't Hof W. Bolscher J.G.M. Poustka A. Nieuw Amerongen A.V. Mollenhauer J. J. Biol. Chem. 2002; 277: 32109-32115Abstract Full Text Full Text PDF PubMed Scopus (123) Google Scholar). The of the bacterial were at at 37 °C for These were at three of the of have defined the binding site within by the bacteria binding of a of overlapping peptides from residues to to of the SRCR domain consensus sequence Only peptides and to bound bacteria in the the motif within peptides also bound to bacteria and was to as of this either at the amino or the peptides bacteria binding and the DMBT1, DMBT1pbs1 bound to mutans and S. as well as to bacteria coli and H. SRCRP2, the agglutination of S. mutans was with the of DMBT1pbs1 the agglutination of S. mutans was of and bacterial S. mutans was with SRCRP2, DMBT1pbs1 150 or and agglutination was at agglutination was at agglutination was DMBT1pbs1 bacterial agglutination of S. gordonii and E. coli and H. DMBT1pbs1 three of in residues in DMBT1pbs1 for bacteria binding, a alanine substitution scan was A of peptides was synthesized in which the DMBT1pbs1 in its was for This peptide was tested in the to S. mutans was by substitution of and the of the The in the SRCR of DMBT1 DMBT1pbs1 peptide is in of the SRCR domains of the bacteria binding of the within the SRCR domains, the peptides were synthesized and Only the in which residues are different from the consensus not bind to bacteria of the Bacteria of within of the SRCR SRCR domains are highly conserved we investigated DMBT1pbs1-corresponding sequences in other SRCR proteins also bacteria binding. the SRCR proteins were SRCR domains. For the consensus sequence of its SRCR domains was and the motif to DMBT1pbs1 was In this a number of 11-mer peptides covering the consensus sequences of different SRCR proteins were tested for bacteria binding. Only the peptides derived from DMBT1 and DMBT1 orthologues as mouse the rat the rabbit and the gallbladder bound bacteria In the study we the minimal bacteria-binding site of DMBT1 and domains in other SRCR proteins also bacteria binding. By a of overlapping peptides, the minimal bacteria-binding site was pinpointed as an 11-amino acid designated substitution of and in a of bacteria binding. These residues are highly conserved within the SRCR domains of DMBT1, the the presence of in domains 1 and In previous we have that DMBT1SAG bacteria in a (17Bikker F.J. Ligtenberg A.J.M. Nazmi K. Veerman E.C.I. Van't Hof W. Bolscher J.G.M. Poustka A. Nieuw Amerongen A.V. Mollenhauer J. J. Biol. Chem. 2002; 277: 32109-32115Abstract Full Text Full Text PDF PubMed Scopus (123) Google Scholar). that the critical role of and in bacteria binding the by their The to substitution of the three residues is in this have on this that a is for bacteria binding. This is by the that the of by the more as in the SRCR domain 1 has of the SRCR consensus domain using overlapping peptides showed that peptides were of bacteria binding. with the of this the SRCR this to an role for this the substitution of by In of the this is by that the of a charged at by the of to The of binding by the DMBT1pbs1 motif of SRCR domain is not because this domain with the other SRCR domains of its in the within two domains does not a role in bacteria binding, which is by the other SRCR domains. The DMBT1pbs1 11-mer peptide agglutination more the peptide This be by the that has a DMBT1pbs1 in a and thus a for the negatively charged bacterial The first three amino acids of the peptide were homologous with the bacteria binding site on the SRCR domain of MARCO (6Brännström A. Sankala M. Tryggvason K. Pikkarainen T. Biochem. Biophys. Res. Commun. 2002; 290: 1462-1469Crossref PubMed Scopus (60) Google Scholar). bacteria binding are on the SRCR domains of the the in this different bacteria binding DMBT1pbs1 does not the and substitution of in DMBT1pbs1 not in the of binding. The charged RXR motif of MARCO an interaction with the negatively charged bacterial In DMBT1pbs1, a negatively charged and the residues and are for bacteria binding. with peptides of other SRCR consensus sequences showed that highly homologous as those in DMBT1 bacteria binding SRCR consensus sequences of other P. marinus WC1, and of the minimal bacteria binding motif but not bind to These in to the presence of the a of DMBT1pbs1 is for bacteria binding. For the of by not the by as in in a the of a Pema-SRCR contains the critical this that Trp have a with to the VEVL for bacteria binding. This of DMBT1pbs1 to the substitution of residues the for proteins to be tested for of bacteria binding. SRCR domains are in proteins of studied the of of the amino acids in SRCR domains by using B. J. S. Google Scholar) in with the This study revealed that and of DMBT1pbs1 are highly conserved the SRCR that residues are for the structure and of SRCR domains. the of bacteria binding was for DMBT1 and its orthologues by this motif These that conserved residues, which to be in the alanine substitution scan, were also for bacteria binding. SRCR proteins are involved in different of binding Grønlund J. O. Madsen J. Holmskov U. F. Immunol. PubMed Google Scholar), the conserved residues in DMBT1pbs1 form a binding motif of SRCR proteins in DMBT1 has into a bacteria binding motif. the of the SRCR Holmskov identified P. marinus as the with a DMBT1 U. Mollenhauer J. Madsen J. Vitved L. Grønlund J. Tornøe I. Kliem A. Reid K.B. Poustka A. Skjødt K. Proc. Natl. Acad. Sci. U. S. A. 1999; 96: 10794-10799Crossref PubMed Scopus (189) Google Scholar). The consensus sequence of this protein the DMBT1pbs1 binding binding for this peptide was to the Pema-SRCR DMBT1 orthologues have been characterized in for in the in the in the and gallbladder to be investigated DMBT1 orthologues are in and proteins are involved in bacteria binding in In we have the minimal bacteria-binding site on the SRCR domains of DMBT1 to an 11-mer and we have identified a number of critical residues within this sequence in this motif the SRCR bacteria binding by this motif is thus to DMBT1