PARENT SESSION
PLATFORM SESSION 6: MOLECULAR BIOLOGY OF MALE AND FEMALE GAMETES
Chair: Sutovsky, Peter¹, ¹
Co-chair: Swain, Jason¹, ¹
Harborside D
4:30 PM-6:30 PM

(40) SLLP1, A NOVEL NON-BACTERIOLYTIC C LYSOZYME-LIKE PROTEIN IN THE ACROSOME OF HUMAN SPERMATOZOA.

Mandal, Arabinda¹, Klotz, Kenneth¹, Shetty, Jagathpala¹, Jayes, Friederike¹, Wolkowicz, Michael¹, Bolling, Laura¹, Coonrod, Scott¹, Black, Michael², Diekman, Alan¹, Haystead, Timothy³, Flickinger, Charles¹, Herr, John¹, ¹ University of Virginia, Charlottesville, VA² University of Virginia, Charlottesville, VA³ Duke University Medical Center, Durham, NC

ABSTRACT- To identify novel proteins, human sperm proteome was analyzed by microsequencing of 2D IEF/SDS-PAGE resolved protein spots. This approach identified several c lysozyme like overlapping peptides from two low molecular weight spots (~15 kDa, pI ~5.0 - 5.2). A full length cDNA was cloned by RACE PCR, encoding a protein named SLLP1, of 23.4 kDa and a pI of 8.0 with a predicted protease cleavage site between A87 and K88. Antisera to the c-terminal 128 aa after the protease cleavage site, identified a processed protein of only ~14 kDa and localized SLLP1 to the acrosome of ejaculated sperm by IF and by immuno-electron microscopy. A significant decrease (54%; P < 0.001; N = 32) in the number of sperm bound to zona free hamster eggs was observed in presence of SLLP1 antisera, suggesting that this antigen is exposed on the sperm acrosome prior to fertilization. SLLP1 mRNA (size ~1 kb) appeared to be expressed in testis and in the Burkitt's lymphoma Raji cell line but a smaller transcript of ~0.8 kb was also detected in pancreas. The gene encoding SLLP1 is located at 17q11.2 and its exon-intron organization corresponding to the processed form is similar to c type (chicken or conventional) lysozyme. C lysozymes are bacteriolytic and posses multiple N-acetylglucosamine binding sites. Most of the invariant residues (17 out of 20), including all the cysteines, and the N-acetylglucosamine binding residues (5 out of 6) of c lysozymes were conserved in SLLP1, however two catalytic residues of c lysozymes were lacking. As expected, based on its sequence, the processed protein expressed in and secreted from yeast showed no bacteriolytic activity. Owing to the typical c lysozyme like sequence, genomic organization, the conservation of substrate binding residues and localization in the acrosomal matrix, we hypothesize that SLLP1 could be a potential binding molecule for interaction with the ZP oligosaccharide residue, N-acetylglucosamine. This work was supported in part by grants from Fogarty International Center D43 TW/HD 00654, NIH HD U54 29099, P30 28934, the Andrew W. Mellon Foundation, and Schering AG.

KEY WORDS: Human, Sperm, c Lysozyme, Acrosome