Abstract
A novel lectin structure was found for a 17-kDa α-D-galactose-binding lectin (termed "MytiLec") isolated from the Mediterranean mussel, Mytilus galloprovincialis. The complete primary structure of the lectin was determined by Edman degradation and mass spectrometric analysis. MytiLec was found to consist of 149 amino acids with a total molecular mass of 16,812.59 Da by Fourier transform-ion cyclotron resonance mass spectrometry, in good agreement with the calculated value of 16,823.22 Da. MytiLec had an N terminus of acetylthreonine and a primary structure that was highly novel in comparison with those of all known lectins in the structure database. The polypeptide structure consisted of three tandem-repeat domains of ∼50 amino acids each having 45-52% homology with each other. Frontal affinity chromatography technology indicated that MytiLec bound specifically to globotriose (Gb3; Galα1-4Galβ1-4Glc), the epitope of globotriaosylceramide. MytiLec showed a dose-dependent cytotoxic effect on human Burkitt lymphoma Raji cells (which have high surface expression of Gb3) but had no such effect on erythroleukemia K562 cells (which do not express Gb3). The cytotoxic effect of MytiLec was specifically blocked by the co-presence of an α-galactoside. MytiLec treatment of Raji cells caused increased binding of anti-annexin V antibody and incorporation of propidium iodide, which are indicators of cell membrane inversion and perforation. MytiLec is the first reported lectin having a primary structure with the highly novel triple tandem-repeat domain and showing transduction of apoptotic signaling against Burkitt lymphoma cells by interaction with a glycosphingolipid-enriched microdomain containing Gb3.
Highlights
The lamina propria was the site of a dense monomorphic cellular infiltration by mature and sometimes atypical plasma cells
Ultrastructural studies confirmed that most cells infiltrating the antral mucosa were typical mature plasma cells
Apart from the presence of Giardia lamblia in duodenal samples, all biopsies obtained by endoscopy, per oral capsule or surgery from small and large intestine, rectum and rS f f
Summary
Multiple gastric biopsies were obtained during endoscopies in March and October 1983. Multilevel biopsies of the duodenum, jejunum, and ileum (per oral capsule), rectum and colon were done in March and October 1983. In April 1983, a full thickness antral biopsy, five multilevel wedge biopsies of the jejunum and ileum, several mesenteric and mesocolon lymph nodes, right hepatic wedge biopsy, and iliac crest biopsy were obtained during laparotomy. Peripheral venous blood, 24 hour urine and fasting gastric juice were sampled in March and October 1983 for immunologic studies. Tissues were fixed in Bouin's fluid and 3 .tm sections were stained by haematoxylin-phloxin-saffran, Giemsa, Mac Manus (PAS) and Alcian blue methods. Tissues were fixed in glutaraldehyde, postfixed in osmium tetroxide, embedded in Epon and thin sections were stained by uranyl acetate and lead citrate
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