PubMed · 11190672
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A P May, E Y Jones. 2001. Sialoadhesin structure.. https://doi.org/10.1007/978-3-540-46410-5_8
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The structural organization of PFA, a novel beta-galactose-specific agglutinin from the snail Pomacea flagellata, was partially characterized. Using mass spectrometry, the molecular weight of this glycoprotein was determined as 32,444 Da (7.4% carbohydrate). The agglutinin was found to form very large aggregates in solution, which were dissociated to monodisperse native-like dimers upon addition of polyethyleneglycol. The identity of the first 38 and the last 11 residues of the polypeptide chain was determined. It was found that PFA and the N-glycosidase subunit of ricin, a heterodimeric cytotoxin isolated from castor bean seeds, are homologous to each other in the N-terminal region. Furthermore, the far-UV circular dichroism spectra of these proteins were found to be nearly superimposable, evidencing that they share common general features in their secondary and tertiary structures. On the basis of these similarities, it can be concluded that PFA is structurally related to the ribosome-inactivating protein superfamily.
Salivary agglutinin is a 300-400 kDa salivary glycoprotein that binds to antigen B polypeptides of oral streptococci, thereby playing a role in their colonization and the development of caries. A mass spectrum was recorded of a trypsin digest of agglutinin. A dominant peak of 1460 Da was sequenced by quadrupole time-of-flight (Q-TOF) tandem MS. The sequence showed 100% identity with part of the scavenger receptor cysteine-rich ('SRCR') domain found in gp-340/DMBT1 (deleted in malignant brain tumours-1). The mass spectrum revealed 11 peaks with an identical mass as a computer-simulated trypsin digest of gp-340. gp-340 is a 340 kDa glycoprotein isolated from bronchoalveolar lavage fluid that binds specifically to lung surfactant protein-D. DMBT1 is a candidate tumour suppressor gene. A search in the human genome revealed only one copy of this gene. The molecular mass, as judged from SDS/PAGE and the amino acid composition of agglutinin, was found to be nearly identical with that of gp-340. It was shown by Western blotting that monoclonal antibodies against gp-340 reacted with salivary agglutinin, and monoclonals against agglutinin reacted with gp-340. It was demonstrated that gp-340 and agglutinin bound in a similar way to Streptococcus mutans and surfactant protein-D. Histochemically, the distribution of gp-340 in the submandibular salivary glands was identical with the agglutinin distribution, as shown in a previous paper [Takano, Bogert, Malamud, Lally and Hand (1991) Anat. Rec. 230, 307-318]. We conclude that agglutinin is identical with gp-340, and that this molecule interacts with S. mutans and surfactant protein-D.
OBJECTIVES: Hensin induces terminal differentiation in rabbit kidney collecting tubule cells. Rabbit hensin and human DMBT1 result from alternative splicing of the same gene. The human DMBT1 gene is located on chromosome 10q25-26, a region often deleted in prostate cancer. In this study we examined the potential role of this gene in terminal differentiation of prostate, as well as its role in prostatic carcinogenesis. METHODS: We searched for deletions of this gene in prostatic cells cultured from cancer and benign tissues using PCR and cDNA cloning. The expression of hensin/DMBT1 in cultured cells and during prostate development was characterized by immunochemistry. RESULTS: No deletions of hensin/DMBT1 similar to those found in glioblastomas, lung and esophageal cancers were observed in prostate cancer or BPH cells. Hensin/DMBT1 protein was localized in intracellular vesicles of epithelial cells in neonatal and 6-week-old mouse prostates. By 6 weeks, hensin/DMBT1 began to localize in the basal lamina of the prostate and vas deferens. In matured 6-month-old prostates, there was extensive deposition of hensin/DMBT1 in the basal lamina. CONCLUSIONS: There is no evidence that hensin/DMBT1 is implicated in prostatic carcinogenesis. The localization of hensin/DMBT1 during maturation raises the possibility that hensin/DMBT1 is involved in terminal differentiation of the prostate and vas deferens.