PubMed · 6815963
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H Franz, P Ziska, J Mohr. 1982. Lectins--definition and classification.. https://doi.org/10.1016/s0065-1281(82)80006-8
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Salivary agglutinin is encoded by DMBT1 and identical to gp-340, a member of the scavenger receptor cysteine-rich (SRCR) superfamily. Salivary agglutinin/DMBT1 is known for its Streptococcus mutans agglutinating properties. This 300-400 kDa glycoprotein is composed of conserved peptide motifs: 14 SRCR domains that are separated by SRCR-interspersed domains (SIDs), 2 CUB (C1r/C1s Uegf Bmp1) domains, and a zona pellucida domain. We have searched for the peptide domains of agglutinin/DMBT1 responsible for bacteria binding. Digestion with endoproteinase Lys-C resulted in a protein fragment containing exclusively SRCR and SID domains that binds to S. mutans. To define more closely the S. mutans-binding domain, consensus-based peptides of the SRCR domains and SIDs were designed and synthesized. Only one of the SRCR peptides, designated SRCRP2, and none of the SID peptides bound to S. mutans. Strikingly, this peptide was also able to induce agglutination of S. mutans and a number of other bacteria. The repeated presence of this peptide in the native molecule endows agglutinin/DMBT1 with a general bacterial binding feature with a multivalent character. Moreover, our studies demonstrate for the first time that the polymorphic SRCR domains of salivary agglutinin/DMBT1 mediate ligand interactions.
A sperm-agglutinating factor was purified from ovulated carp eggs and the conditioned medium (CM) of cortical-reacted eggs. It was identified to be the carp ovarian cystatin. Three cystatin isoforms were found. The cystatin isolated from the CM had a higher sperm-agglutinating activity than that isolated from eggs, although the cystatins have identical N-terminal amino acid sequences, masses, and positive charges. Differences in sperm-agglutinating activity between the cystatins of the CM and eggs may be caused by the different conformations because they differed in circular dichroism spectrum and tryptic map. Cystatin was discharged from cortical granules to the perivitelline space after fertilization and is abundant in the perivitelline fluid (PVF) of early stage embryos. Cystatin rapidly agglutinated spermatozoa via an electrostatic interaction. Other basic proteins also agglutinated carp spermatozoa. Their activities were inhibited by salt and high pH. Cystatin bound to the entire surface of carp spermatozoa. The PVF of early embryos agglutinated carp spermatozoa. The activity was related to the cystatin content and influenced by ionic strength and pH. Therefore, cystatin is the major sperm-agglutinating factor of PVF. Owing to the rapid action of cystatin on spermatozoa agglutination and the presence of a high concentration of cystatin in PVF, cystatin is considered important for preventing polyspermy in carp eggs.
Campylobacter jejuni has been identified as the leading cause of acute bacterial diarrhea in the United States, yet compared with other enteric pathogens, considerably less is understood concerning the virulence factors of this human pathogen. A random in vivo transposon mutagenesis system was recently developed for the purpose of creating a library of C. jejuni transformants. A total of 1,065 C. jejuni transposon mutants were screened for their ability to swarm on motility agar plates and autoagglutinate in liquid cultures; 28 mutants were subsequently identified. The transposon insertion sites were obtained by using random-primed PCR, and the putative genes responsible for these phenotypes were identified. Of these mutants, all 28 were found to have diminished motility (0 to 86% that of the control). Seventeen motility mutants had insertions in genes with strong homology to functionally known motility and chemotaxis genes; however, 11 insertions were in genes of unknown function. Twenty motility mutants were unable to autoagglutinate, suggesting that the expression of flagella is correlated with autoagglutination (AAG). However, four mutants expressed wild-type levels of surface FlaA, as indicated by Western blot analysis, yet were unable to autoagglutinate (Cj1318, Cj1333, Cj1340c, and Cj1062). These results suggest that FlaA is necessary but not sufficient to mediate the AAG phenotype. Furthermore, two of the four AAG mutants (Cj1333 and Cj1062) were unable to invade INT-407 intestinal epithelial cells, as determined by a gentamicin treatment assay. These data identify novel genes important for motility, chemotaxis, and AAG and demonstrate their potential role in virulence.