MBE Advance Access originally published online on November 3, 2004
Molecular Biology and Evolution 2005 22(3):533-541; doi:10.1093/molbev/msi037
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Research Article |
Positive Selection in the Carbohydrate Recognition Domains of Sea Urchin Sperm Receptor for Egg Jelly (suREJ) Proteins
* Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California San Diego, La Jolla; and Department of Genome Sciences, University of Washington, Seattle
E-mail: vvacquier{at}ucsd.edu.
A wealth of evidence shows that protein-carbohydrate recognition mediates the steps of gamete interaction during fertilization. Carbohydrate-recognition domains (CRDs) comprise a large family of ancient protein modules of approximately 120 amino acids, having the same protein fold, that bind terminal sugar residues on glycoproteins and polysaccharides. Sea urchin sperm express three suREJ (sea urchin receptor for egg jelly) proteins on their plasma membranes. suREJ1 has two CRDs, whereas suREJ2 and suREJ3 both have one CRD. suREJ1 binds the fucose sulfate polymer (FSP) of egg jelly to induce the sperm acrosome reaction. The structure of FSP is species specific. Therefore, the suREJ1 CRDs could encode molecular recognition between sperm and egg underlying the species-specific induction of the acrosome reaction. The functions of suREJ2 and suREJ3 have not been explored, but suREJ3 is exclusively localized on the plasma membrane over the sperm acrosomal vesicle and is physically associated with sea urchin polycystin-2, a known cation channel. An evolutionary analysis of these four CRDs was performed for six sea urchin species. Phylogenetic analysis shows that these CRDs were already differentiated in the common ancestor of these six sea urchins. The CRD phylogeny agrees with previous work on these species based on one nuclear gene and several mitochondrial genes. Maximum likelihood shows that positive selection acts on these four CRDs. Threading the suREJ CRDs onto the prototypic CRD crystal structure shows that many of the sites under positive selection are on extended loops, which are involved in saccharide binding. This is the first demonstration of positive selection in CRDs and is another example of positive selection acting on the evolution of gamete-recognition proteins.
Key Words: positive selection • fertilization • acrosome reaction • sperm lectins • sperm receptors • C-type lectins • maximum likelihood • sexual antagonism
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  C. Riginos, D. Wang, and A. J. Abrams Geographic Variation and Positive Selection on M7 Lysin, an Acrosomal Sperm Protein in Mussels (Mytilus spp.) Mol. Biol. Evol., October 1, 2006; 23(10): 1952 - 1965. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 H. Ichihara, K.-i. Kuma, and H. Toh Positive Selection in the ComC-ComD System of Streptococcal Species. J. Bacteriol., September 1, 2006; 188(17): 6429 - 6434. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. M. Turner and H. E. Hoekstra Adaptive Evolution of Fertilization Proteins within a Genus: Variation in ZP2 and ZP3 in Deer Mice (Peromyscus) Mol. Biol. Evol., September 1, 2006; 23(9): 1656 - 1669. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. R. Levitan and D. L. Ferrell Selection on gamete recognition proteins depends on sex, density, and genotype frequency. Science, April 14, 2006; 312(5771): 267 - 269. [Abstract] [Full Text] [PDF]
|
|