An acrosomal protein, sp32, in mammalian sperm is a binding protein specific for two proacrosins and an acrosin intermediate.
An acrosomal protein, sp32, in mammalian sperm is a binding protein specific for two proacrosins and an acrosin intermediate.
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DOI：
10.1016/s0021-9258(17)37000-x
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发表时间：
1994-04
期刊：
影响因子：
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通讯作者：
Tadashi BabaS;Yasushi Niida;Y. Michikawa;S. Kashiwabara;K. Kodaira;M. Takenaka;N. Kohno;George L. Gertong;Y. Arai
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文献类型：
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作者：
Tadashi BabaS;Yasushi Niida;Y. Michikawa;S. Kashiwabara;K. Kodaira;M. Takenaka;N. Kohno;George L. Gertong;Y. Arai
从猪精的酸提取物中完全纯化了顶体蛋白sp32。纯化后的sp32在sds -聚丙烯酰胺凝胶电泳上显示出一条32 kda的单蛋白带，并被鉴定为55-、53-和49 kda形式的（原）顶蛋白特异性结合蛋白。该蛋白不能结合43-kDa的顶蛋白中间体和35-kDa的成熟顶蛋白。sp32在体外碱性pH条件下显著加速了原acrosin的自激活，影响了原acrosin的成熟途径。在sp32存在的情况下，55- kda和53-kDa的前顶蛋白中间体积累49-kDa，而不是43-kDa的顶蛋白中间体。这些结果表明sp32与53-kDa原顶蛋白的氨基端和羧基端都有相互作用。从猪和豚鼠睾丸的lambda gt11 cDNA文库中分别鉴定出了编码猪和豚鼠sp32的cDNA克隆。推导出的氨基酸序列表明，sp32最初是作为一个61 kda的前体蛋白合成的，在氨基端有一个假定的信号肽。前体分子的羧基末端对应于成熟的sp32。因此，sp32是由前体的翻译后修饰产生的。sp32与顶体酶原的结合可能参与了顶体酶原包装到顶体基质中的过程。
An acrosomal protein, sp32, was completely purified from acid extracts of ejaculated porcine sperm. Purified sp32 gave a single 32-kDa protein band on SDS-polyacrylamide gel electrophoresis and was characterized as a binding protein specific for 55-, 53-, and 49-kDa forms of (pro)acrosin. This protein was not capable of binding a 43-kDa acrosin intermediate and 35-kDa mature acrosin. sp32 significantly accelerated autoactivation of proacrosin at a basic pH in vitro and affected the maturation pathway of proacrosin. In the presence of sp32, the 49-kDa acrosin intermediate from the 55- and 53-kDa proacrosins was accumulated, instead of the 43-kDa acrosin intermediate. These results suggest that sp32 interacts with both the amino- and carboxyl-terminal sequences of the 53-kDa proacrosin. The cDNA clones coding for porcine and guinea pig sp32 have been identified from testis cDNA libraries in lambda gt11. The deduced amino acid sequence indicates that sp32 is initially synthesized as a 61-kDa precursor protein with a putative signal peptide at the amino terminus. The carboxyl-terminal half of the precursor molecule corresponds to the mature sp32. Thus, sp32 is produced by post-translational modification of the precursor. The binding of sp32 to proacrosin may be involved in packaging the acrosin zymogen into the acrosomal matrix.