Abstract
Sulfated polysaccharides from egg jelly are the molecules responsible for inducing the sperm acrosome reaction in sea urchins. This is an obligatory event for sperm binding to, and fusion with, the egg. The sulfated polysaccharides from sea urchins have simple, well defined repeating structures, and each species represents a particular pattern of sulfate substitution. Here, we examined the egg jellies of the sea urchin sibling species Strongylocentrotus droebachiensis and Strongylocentrotus pallidus. Surprisingly, females of S. droebachiensis possess eggs containing one of two possible sulfated fucans, which differ in the extent of their 2-O-sulfation. Sulfated fucan I is mostly composed of a regular sequence of four residues ([4-alpha-l-Fucp-2(OSO3)-1-->4-alpha-l-Fucp-2(OSO3)-1-->4-alpha-l-Fucp-1-->4-alpha-l-Fucp-1]n), whereas sulfated fucan II is a homopolymer of 4-alpha-l-Fucp-2(OSO3)-1 units. Females of S. pallidus contain a single sulfated fucan with the following repeating structure: [3-alpha-l-Fucp-2(OSO3)-1-->3-alpha-l-Fucp-2(OSO3)-1-->3-alpha-l-Fucp-4(OSO3)-1-->3-alpha-l-Fucp-4(OSO3)-1]n. The egg jellies of these two species of sea urchins induce the acrosome reaction in homologous (but not heterologous) sperm. Therefore, the fine structure of the sulfated alpha-fucans from the egg jellies of S. pallidus and S. droebachiensis, which differ in their sulfation patterns and in the position of their glycosidic linkages, ensures species specificity of the sperm acrosome reaction and prevents interspecies crosses. In addition, our observations allow a clear appreciation of the common structural features among the sulfated polysaccharides from sea urchin egg jelly and help to identify structures that confer finer species specificity of recognition in the acrosome reaction.
Highlights
Summary of Variants of Sulfated ␣-L-Fucans from Sea Urchin Egg Jelly—A variety of sulfated fucans have been described in marine algae (29 –31)
The algal fucans have complex, heterogeneous structures. Their regular repeating sequences are not deduced; even high-field NMR is at the limit of its resolution, and complete description of their structure is not available at present [9, 27]
We isolated and characterized several sulfated ␣-L-fucans from echinoderms, mostly from sea urchin egg jelly
Summary
Sulfated polysaccharides, the potency of acrosome reaction induction clearly depends on the extent of 2-O- and 4-O-sulfation in the chain of 3-linked ␣-L-fucopyranosyl units [7]. We extend our studies to two new sea urchins, the closely related species Strongylocentrotus droebachiensis and Strongylocentrotus pallidus, which both have a circumarctic distribution. The egg jellies of these sea urchins contain sulfated ␣-fucans with new structures. Our results show expanded possibilities for structural variation among sulfated ␣-L-fucans from echinoderms and possible biological and evolutionary implications of these unique polysaccharides. Detailed structural characterizations help evaluate the therapeutic potential of sulfated polysaccharides, as already demonstrated for the anticoagulant activity of sulfated fucans [9] and sulfated galactans [10]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
