Cell aggregation in the marine sponge Microciona prolifera is mediated by a multimillion molecular-mass aggregation factor, termed MAF. Earlier investigations revealed that the cell aggregation activity of MAF depends on two functional domains: (i) a Ca2+-independent cell-binding domain and (ii) a Ca2+-dependent proteoglycan self-interaction domain. Structural analysis of involved carbohydrate fragments of the proteoglycan in the self-association established a sulfated disaccharide β-d-GlcpNAc3S- (1→3)-α-l-Fucp and a pyruvated trisaccharide β-d-Galp4,6(R)Pyr- (1→4)-β-d-GlcpNAc-(1→3)-α-l-Fucp. Recent UV, SPR, and TEM studies, using BSA conjugates and gold nanoparticles of the synthetic sulfated disaccharide, clearly demonstrated self-recognition on the disaccharide level in the presence of Ca2+-ions. To determine binding forces of the carbohydrate-carbohydrate interactions for both synthetic MAF oligosaccharides, atomic force microscopy (AFM) studies were carried out. It turned out that, in the presence of Ca2+-ions, the force required to separate the tip and sample coated with a self-assembling monolayer of thiol-spacer-containing β-d-GlcpNAc-(1→3)-α-l-Fucp-(1→O)(CH2) 3S(CH2)6S- was found to be quantized in integer multiples of 30∈±∈6 pN. No binding was observed between the two monolayers in the absence of Ca2+-ions. Cd2+-ions could partially induce the self-interaction. In contrast, similar AFM experiments with thiol-spacer-containing β-d-Galp4,6(R)Pyr-(1→4)- β-d-GlcpNAc-(1→3)-α-l-Fucp-(1→O)(CH2) 3S(CH2)6S- did not show a binding in the presence of Ca2+-ions. Also TEM experiments of gold nanoparticles coated with the pyruvated trisaccharide could not make visible aggregation in the presence of Ca2+-ions. It is suggested that the self-interaction between the sulfated disaccharide fragments is stronger than that between the pyruvated trisaccharide.
CITATION STYLE
Carvalho De Souza, A., Ganchev, D. N., Snel, M. M. E., Van Der Eerden, J. P. J. M., Vliegenthart, J. F. G., & Kamerling, J. P. (2009). Adhesion forces in the self-recognition of oligosaccharide epitopes of the proteoglycan aggregation factor of the marine sponge Microciona prolifera. Glycoconjugate Journal, 26(4), 457–465. https://doi.org/10.1007/s10719-008-9196-7
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