Purification and characterization of a midgut lectin-trypsin complex from the tsetse fly Glossina longipennis.
A blood-meal-induced lectin (agglutinin) with proteolytic activity was isolated from midgut extracts of Glossina longipennis by a two-step procedure involving anion-exchange chromatography. It is a glycoprotein [native molecular weight (M(r) 61,000 +/- 3000 da) composed of two noncovalently-linked subunits designated alpha (M(r), approximately 27,000 da) and beta (M(r), approximately 33,000 da). The trypsin activity and the glycosyl residues were present on the alpha- and beta-subunits, respectively. The native protein was capable of agglutinating both bloodstream-form and procyclic trypanosomes as well as rabbit red blood cells. This activity was strongly inhibited by D-glucosamine and weakly inhibited by N-acetyl-D-glucosamine. Similarly, soybean trypsin inhibitor abrogated agglutination of bloodstream-form parasites, whereas the procyclics were unaffected. The agglutination activity was sensitive to temperatures above 40 degrees C but was unaffected by chelators of metal ions. Antibodies raised against the protein were used in immunoblotting experiments to show the presence of a similar protein in several members of the Glossina species. However, no cross-reactivity was detected with midgut extracts prepared from sandflies, mosquitoes, or stable flies. It is proposed that this molecule might play an important role in differentiation of bloodstream-form trypanosomes into procyclic (midgut) forms.
Osir
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International Centre of Insect Physiology and Ecology, Nairobi, Kenya.
Abubakar
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Imbuga
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D000117:Acetylglucosamine / Q000494:pharmacology; D000371:Agglutination / Q000187:drug effects; D000372:Agglutination Tests; D000818:Animals; D002852:Chromatography, Ion Exchange; D005944:Glucosamine / Q000494:pharmacology; D006790:Host-Parasite Interactions; D015151:Immunoblotting; D019476:Insect Proteins; D007303:Insect Vectors / Q000737:chemistry* / Q000201:enzymology / Q000469:parasitology; D037102:Lectins / Q000737:chemistry* / Q000378:metabolism; D008297:Male; D051381:Rats; D013045:Species Specificity; D013696:Temperature; D014346:Trypanosoma brucei brucei / Q000187:drug effects / Q000502:physiology; D014357:Trypsin / Q000378:metabolism; D014361:Trypsin Inhibitors / Q000494:pharmacology; D014370:Tsetse Flies / Q000737:chemistry* / Q000201:enzymology / Q000469:parasitology
D019476:Insect Proteins; D037102:Lectins; D014361:Trypsin Inhibitors; C094852:midgut lectin, Glossina; D014357:Trypsin; D005944:Glucosamine; D000117:Acetylglucosamine