Testicular protein Spag5 has similarity to mitotic spindle protein Deepest and binds outer dense fiber protein Odf1.
Outer dense fibers (ODF) and the fibrous sheath (FS) are major cytoskeletal structures in the mammalian sperm tail. The molecular mechanisms underlying their morphogenesis along the axoneme or their function are poorly understood. Recently, we reported the cloning and characterization of Odf2, a major ODF protein, and Spag4, an axoneme-binding protein, by virtue of their strong interaction with Odf1, the 27 kDa major ODF protein. We proposed a crucial role for leucine zippers in molecular interactions during sperm tail morphogenesis. Here we report the cloning and characterization of a novel gene, Spag5, which encodes a 200 kDa testicular protein that interacts strongly with Odf1. Spag5 is transcribed and translated in pachytene spermatocytes and spermatids. It bears 73% similarity with the mitotic spindle protein Deepest of unknown function. We identified two putative leucine zippers in the C-terminal part of the Spag5 protein, the downstream one of which is involved in interaction with Odf1. Interestingly, these motifs are present in Deepest. These results highlight the importance of the leucine zipper in sperm tail protein interactions. Mol. Reprod. Dev. 59: 410-416, 2001.
Shao
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Department of Biochemistry and Molecular Biology, University of Calgary, 3330 Hospital Drive N.W., Calgary, Alberta, Canada T2N 4N1. fvdhoorn@ucalgary.ca
Xue
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van der Hoorn
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D000595:Amino Acid Sequence; D000818:Animals; D015152:Blotting, Northern; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015723:Gene Library; D006360:Heat-Shock Proteins; D016350:Leucine Zippers; D008297:Male; D008969:Molecular Sequence Data; D011485:Protein Binding; D011506:Proteins / Q000737:chemistry / Q000378:metabolism*; D051381:Rats; D013082:Sperm Tail / Q000737:chemistry / Q000378:metabolism; D013087:Spermatids / Q000378:metabolism*; D013090:Spermatocytes / Q000378:metabolism*; D008941:Spindle Apparatus / Q000737:chemistry; D013737:Testis / Q000737:chemistry* / Q000166:cytology; D020798:Two-Hybrid System Techniques
D002352:Carrier Proteins; D006360:Heat-Shock Proteins; C490108:Odf1 protein, rat; C490105:Odf2 protein, rat; D011506:Proteins; C436025:Spag5 protein, rat