Calcium ions stabilize a protein structure of hemolytic lectin CEL-III from marine invertebrate Cucumaria echinata.
CEL-III, a galactose/N-acetylgalactosamine (Gal/GalNAc)-specific lectin purified from a marine invertebrate, Cucumaria echinata, has a strong hemolytic activity, especially toward human and rabbit erythrocytes in the presence of Ca2+. We evaluated the role of Ca2+ in hemagglutinating and hemolytic activities of CEL-III. We found that Ca2+ is closely associated with both activities of CEL-III. The fluorescence spectra of CEL-III upon binding to Ca2+ were measured. The result showed a structural change of CEL-III in the presence of Ca2+. The structural change of CEL-III upon Ca2+ binding was further demonstrated by stabilization against urea denaturation and by insusceptibility to protease digestions. CEL-III was completely unfolded at a low concentration of 2 M urea, while CEL-III complexed with Ca2+ was stable in 6 M urea. As for protease digestions, CEL-III monomer and oligomer were readily digested by trypsin, chymotrypsin, and papain in the absence of Ca2+, while they were insusceptible to the three proteases in the presence of Ca2+. The papain digestion of the decalcified oligomer produced a large C-terminal peptide, suggestting that the C-terminal region of CEL-III may participate in oligomerization of CEL-III as a core domain.
Sallay
I
I
Department of Bioscience and Biotechnology, Faculty of Agriculture, Graduate School, Kyushu University, Fukuoka, Japan.
Tojo
S
S
Nomiyama
K
K
Kouzuma
Y
Y
Kimura
M
M
Yamasaki
N
N
D000818:Animals; D002118:Calcium / Q000737:chemistry*; D004912:Erythrocytes / Q000187:drug effects; D006384:Hemagglutination / Q000187:drug effects*; D006461:Hemolysis / Q000187:drug effects*; D006868:Hydrolysis; D066298:In Vitro Techniques; D037102:Lectins / Q000737:chemistry* / Q000494:pharmacology; D011489:Protein Denaturation; D011817:Rabbits; D012616:Sea Cucumbers / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D014508:Urea / Q000737:chemistry
C402644:CEL-III lectin, Cucumaria echinata; D037102:Lectins; D014508:Urea; D002118:Calcium