A GPI-anchored sea urchin sperm membrane protein containing EGF domains is related to human uromodulin.
An Mr 63-kD sea urchin sperm flagellar membrane protein has been previously implicated as a possible receptor for egg jelly ligand(s) that trigger the sperm acrosome reaction (AR). The cDNA and deduced amino acid sequences of the 63-kD protein are presented. The open reading frame codes for a protein of 470 amino acids which contains a putative signal sequence of 25 residues. Western blots using antibodies to two synthetic peptides confirm the sequence to be that of the 63-kD protein. The mRNA is approximately 2,300 bases in length and the gene appears to be single copy. The protein is released from sperm membrane vesicles by treatment with phosphatidylinositol-specific phospholipase C, showing that it is anchored to the flagellar membrane by glycosylphosphatidyl inositol (GPI). Although we cannot demonstrate involvement of the 63-kD protein in the AR, it is of potential interest because it shares significant similarity with the developmentally expressed proteins crumbs, notch and xotch as well as human uromodulin over a region that includes two separate EGF repeats.
Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, San Diego, La Jolla 92093-0202.
L M
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Mendoza
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Nishioka
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Vacquier
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D004815:Epidermal Growth Factor; D005260:Female; D017261:Glycosylphosphatidylinositols; D008297:Male; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics*; D008969:Molecular Sequence Data; D009088:Mucoproteins; D012617:Sea Urchins / Q000737:chemistry* / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D013084:Sperm-Ovum Interactions; D013094:Spermatozoa / Q000737:chemistry*; D058949:Uromodulin
D017261:Glycosylphosphatidylinositols; D008565:Membrane Proteins; D009088:Mucoproteins; C548612:UMOD protein, human; D058949:Uromodulin; D004815:Epidermal Growth Factor