1jc9
From Proteopedia
TACHYLECTIN 5A FROM TACHYPLEUS TRIDENTATUS (JAPANESE HORSESHOE CRAB)
Structural highlights
Function[TL5A_TACTR] Lectin involved in innate immunity. Agglutinates all types of human erythrocytes, Gram-positive and Gram-negative bacteria. Has a stronger agglutinating activity towards Gram-negative bacteria than towards Gram-positive bacteria. Specifically recognizes acetyl group-containing substances on agglutinated cells. The hemagglutinating activity was inhibited by EDTA, acetyl group-containing mono- and disaccharides, N-acetyl derivatives of amino acids, other acetyl group-containing substances, propionamide and benzamide. Enhances the antimicrobial activity of big defensin against Gram-positive bacteria but not against Gram-negative bacteria.[1] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedBecause invertebrates lack an adaptive immune system, they had to evolve effective intrinsic defense strategies against a variety of microbial pathogens. This ancient form of host defense, the innate immunity, is present in all multicellular organisms including humans. The innate immune system of the Japanese horseshoe crab Tachypleus tridentatus, serving as a model organism, includes a hemolymph coagulation system, which participates both in defense against microbes and in hemostasis. Early work on the evolution of vertebrate fibrinogen suggested a common origin of the arthropod hemolymph coagulation and the vertebrate blood coagulation systems. However, this conjecture could not be verified by comparing the structures of coagulogen, the clotting protein of the horseshoe crab, and of mammalian fibrinogen. Here we report the crystal structure of tachylectin 5A (TL5A), a nonself-recognizing lectin from the hemolymph plasma of T. tridentatus. TL5A shares not only a common fold but also related functional sites with the gamma fragment of mammalian fibrinogen. Our observations provide the first structural evidence of a common ancestor for the innate immunity and the blood coagulation systems. The 2.0-A crystal structure of tachylectin 5A provides evidence for the common origin of the innate immunity and the blood coagulation systems.,Kairies N, Beisel HG, Fuentes-Prior P, Tsuda R, Muta T, Iwanaga S, Bode W, Huber R, Kawabata S Proc Natl Acad Sci U S A. 2001 Nov 20;98(24):13519-24. Epub 2001 Nov 13. PMID:11707569[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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